An exhibition in Vienna probes our attitude towards nudity - people in the West have become accustomed to the naked female form, but male nudes can still shock. Before the show opened, the museum even covered up parts of its own posters, saying they had caused public outrage.

Five naked male statues on a pedestal confront you as you enter the new exhibition at the Leopold Museum.

The earliest is Ancient Egyptian, and the most recent a figure based on a shopping mannequin.

Tobias Natter, the director of the Leopold Museum, says the opening display is a "walk through 5,000 years of history".

"You have an old Egyptian nude, which is very unusual for Egyptian art, you have Roman art, you have Rodin from the 19th and 20th Century, to a postmodern statue. It tells the visitor the male nude in art has a very long tradition," he says.

The exhibition features a diverse range of styles, from paintings by Peter Paul Rubens, Paul Cezanne, Edvard Munch and the expressionist artist Egon Schiele, to more modern and sexually explicit works by the US photographer Robert Mapplethorpe and the London-based artists Gilbert and George.

There are images of erect penises, and of anuses.

Natter says the museum is breaking new ground.

We are not used to seeing a penis - I think that is the main problem for people Erich Kocina

"It's quite unusual for an exhibition to focus on the depiction of the male nude. Surprisingly we had many exhibitions dealing with the female nude body, but so far never an exhibition which features the male nude. Somehow it is a taboo.

"On the other hand, we see that the male nude is getting a new presence in modern contemporary society. He is now on posters, he is on stages, he is getting more and more normal."

An image of naked woman is still regarded in a very different light from that of a naked man, Natter says.

"We saw with the advertising for our exhibition, there is still a difference between a female nude body on the poster or a male nude body. This makes a cultural difference that is still on-going and needs to be discussed with an exhibition."

One of the posters advertising the exhibit featured a full-frontal photograph of three naked footballers, by the French artists Pierre et Gilles. Shortly before the opening last month, the Leopold Museum said that it had received so many complaints that it had been forced to take action.

It put a red band covering the intimate parts of the footballers, on some - but not all - of the posters.

They are very well-built, they are sportsmen - it's nice to see A passerby comments on the posters

But Vienna is full of posters of naked or semi-naked women and is also known for its relaxed approach to nudity at mixed saunas and sunbathing areas. So did the pictures really cause outrage?

Erich Kocina, from Die Presse newspaper, says the museum expected to provoke controversy with the posters - but it went beyond that, causing serious offence to some Viennese.

"It's a mixture - 30% was marketing and 70% was genuine outrage," he says.

"I think we are just used to seeing naked women because they are used as objects of desire in advertisements and TV. Naked men are not that common - we are not used to seeing a penis. I think that is the main problem for people."

Art historian Eva Kernbauer, from the University of Applied Arts in Vienna, says male nudes have been around for a long time, but the way nude men and women have been depicted has always differed.

Art exposed Western art tends to focus on the naked female form, and expresses sensuality and desire

If we spare a thought for the male nude, says classicist Edith Hall, he tends to symbolise courage and endurance Listen to Edith Hall's Radio 3 essay on nudes In pictures: Nudes in art

"To put it very simply, male nudity was closely linked to strength, invulnerability and heroism, the female nude to beauty and erotics," she says.

"Also, the 'Venus pudica' [the shameful Venus] was already developed in ancient Greece, so the depictions of female chastity and female nudity are historically deeply interlinked. The female nude is not threatening at all - female nudity is vulnerable, because it acknowledges the gaze of the beholder."

This classical model is still powerful today, she says. Female nudity is not only omnipresent, it is also unthreatening. Male nudity is more challenging.

"Male nudity is very often linked to the exposure of sexual organs - the penis - and this is often done in a way that responds to the classical model of aggression and strength.

"While the sexual organ in itself does not necessarily have to appear as threatening or aggressive, the difference from the dominant model of soft female nudity is great."

Despite a long search throughout Vienna, I can't find anybody deeply outraged by the naked posters.

One man tells me guardedly that he is not "highly appreciative" of the image.

"It's provocative, it's true," says a woman named Eva. "On the other hand it is looking back to the old days when nakedness was quite common [in art], so I think we should get used to it."

And others, such as Cecile, a tourist visiting from France, like the nudes.

"They are very well-built, they are sportsmen, it's not like ugly old men with a big belly, so they are pretty. It's nice to see."