Badly fitted condoms do not just reduce the pleasure of sex for men and women - they raise the risks of infection and pregnancy, researchers say.
Men are twice as likely to take the condom off midway through sex due to a poor fit, a poll of 436 men in Sexually Transmitted Infections journal reveals.
Ill-fitting condoms more than doubled the chances of them splitting or slipping off, a Kentucky team found.
UK experts said men should know condoms came in different shapes and sizes.
Condom use is increasing in popularity, now rivalling the Pill as a form of contraception, according to a recent poll.
However, there are concerns that couples may turn away from them if they fail to fit comfortably and correctly, and risk unsafe sex instead.
The latest study fuels these concerns.
Out of 436 men questioned by the University of Kentucky researchers, 195 reported that their last sexual encounter involved an ill-fitting condom.
A total of 120 of these said that this had reduced their own sexual pleasure, and 57 said it had reduced it for their partner.
In addition, 34 said they had removed the condom early, while 18 said the condom had broken during sex.
All of these problems were far less frequent among men who reported a well-fitted condom.
