When I was in Venice last March there seemed to be a "uniform

You must cover your shoulders and knees in churches. Other than that it doesn't much matter.

i believe the key is common sense, jeans are ok, but always try to keep a nice combination of jean with whatever you wear as a top,wear nice casual shoes, not tennis preferably. No one is going to tell you anything but i can vouch it helps to be treated a notch better when checking in etc, or asking for a table. In italy beauty counts , at night in cities it is like New york, and of course it depends of the kind of restaurant you are eating that night.
have fun.

Whoops, touched the wrong button on the computer. Anyway, among the younger ladies, the "uniform" worn was black high-heeled boots, black leggings, black mini-skirt, black sweater, and these really cute, black puffy, but fitted, down jackets. It seemed every girl I saw under 30 years old was wearing the same outfit. The older ladies had on long wool coats so it was difficult to see what was underneath. I don't recall seeing too many people wearing jeans and I didn't see any tennis shoes. The gentlemen usually had dark dress shoes, dark slacks, and a dark overcoat. Some of the younger guys were in dressy jeans. It was very cold and rainy while we were there and I think people were just dressed to stay warm.

We also spent time in Rome and it was a lot more casual and we saw many people in jeans. I live in California and I would say that the Italians definately dress nicer during the day then we do, but we are pretty much equal when it comes to going out to dinner and evening wear.

The big mistake we made was not bringing warm coats for our stay in Venice and we got very cold in the damp rainy weather.

I hoped this helped.

Jeans are fine for day wear - assuming you mean stylish jeans - not out at the knees mow the lawn jeans. Giant white clown sneakers will NOT be worn by locals. When going out to dinner - if the place is not very casuale I would wear something better than jeans - varying depending on how upscale the restaurant is.

EVeryone's - including men's - knees, shoulders and bosoms should be covered to enter churches.

Thank you everyone this helps a lot. It's just as I suspected, we will dress nice.

What a coincidence!! Our family is also traveling to Rome and staying in Positano for a week. I was curious about the attire too...Love wearing heels but I guess this has to be left for the evening dinner.

Have fun!!! We will be traveling may 2013 and can't wait!!!

I'm in Italy now, in Rome and mostly I see are ladies in boots or converse I tried pulling the small heel boots thing off but after a few hours of walking on the cobblestones and doing the tourist thing I'm back at the apartment resting my feet! Don't know how they can be in heels for so many hours

Yes, it's amazing how Italian women can wear heels and walk on cobblestones. Awfully easy to turn an ankle.

I will be in Rome may 2013 too!

It may be quite warm in Rome in May. Capris or light weight slacks might be more comfortable than jeans. Jeans are also heavy to pack so we normally take only one pair in spring and fall and wear lighter clothes much of the time. As for shoes, comfort is the key. Walking surfaces in Italy can be rough so make sure you consider comfort as well as style.

It is likely to be warm and many places don't have air conditioning. You will need lightweight clothes for day, something to keep you dry on the inevitable wet days, and something to pull over at night when the temperature does drop off. Comfortable shoes, of course.

Cleavage, knees, arms and shoulders need to be covered to go into churches, especially the Vatican. Men don't need to worry about cleavage but they can't wear shorts or tank tops.

While middle class Italians seem pretty style conscious, not everyone is middle class, so you will see all sorts of outfits, including some bizarre ones on European and Asian tourists. If you stay in a modest hotel and eat at tourist restaurants no one will care. But it is nice to have the flexibility you have when dressed better.

May could already be very warm. We saw all kinds of outfits, and in the big cities during the day no one really cares. What was most surprising for me were the fashionable looking guys in Capri pants, which I think is a really weird look, but very common in Europe.

I would highly recommend that you bring flats with you. A couple of pairs. The cobblestones in Rome are hard on the feet, but nothing compared to the cobblestones and steep inclines/stairs of Positano.

On my one trip to Venice (in winter, dry weather) I saw almost no local women wearing heels, I imagine because you really must walk everywhere you don't go on a boat. They wore very fashionable low-heeled boots. No idea what they would wear in warm weather--a light open weave oxford would be my choice.

A second generation Italian American friend talks about "fa la bella figura" -- and the women I saw in Italy certainly did. Stylish but always sensible to the weather and place.

The opposite of "bella figura" is "bruta figura" and while people won't necessarily say it, they will certainly think it if it applies.

I explain Italy dressing as 'casual Friday' - not suit and tie or business dress but not shorts, white tennis shoes and baseball caps.
Italians do have a love for clothes and take pride in being stylish.
Shorts are reserved for the beach. You will not see Italian men in shorts in the city.
A great scarf will do multi-duty - over your shoulders to go into a church, twist it into a belt, cover your hair on a windy day, wear it to dress up an outfit.
Comfortable shoes!!!!! Bring 2 pairs so you can swap them out. The cobblestones will do a number on your feet if you're in heels or flats. I take an extra pair of insoles/arch supports that I can switch between shoes. Pamper your feet before bed - wash/dry/lotion and you'll be good to go in the morning.
In May, think layers. Peel off during the day, add back on in the evening or near the water.

I bought my husband zip off pants today! Pants that can zip to shorts by Northface! So, he should be ready for hot and church attending!

Now, for the rest of us, which are women....

"zip off pants"
Do they say "Tourist" across the butt?
Perhaps clothing more appropriate for a safari. Definitely not Rome.

One thing that I definitely noticed in Italy and France is that NO ONE, aside from obvious Americans, was wearing khaki pants. My husband brought them as a nice pair of non-jean pants, but I never saw any Italian men in khakis.