As many as one in 10 young men may have the sexually transmitted infection chlamydia without knowing it, a study suggests.
More than 80,000 people were diagnosed with chlamydia last year
Tests carried out in Scotland on almost 800 army recruits found that 78 were carrying the infection.
The vast majority showed no signs of having chlamydia.
The figures are in line with similar studies on young women, which have suggested that one in 10 also has the infection without knowing it.
Official figures show more and more people are being diagnosed with chlamydia across the UK.
A total of 10,580 cases were reported in Scotland in 2001, the latest year for which figures are available. This was up almost 30% on the previous 12 months.
Chlamydia is now the most common STI in England, Wales and Northern Ireland. In 2001, 71,055 people were diagnosed with the infection, up 10% on the previous year.
An unusual vaginal discharge
Pain when passing urine
Bleeding between periods
Pain during sex or bleeding after sex
Low abdominal pain
There are often no obvious symptoms of chlamydia. But there can be serious long-term complications for women.
It is the most common cause of infertility and ectopic pregnancy. It has also been linked to cervical cancer in women.
The government has stepped up its efforts to combat chlamydia. Ministers in England launched a national screening programme, last year, primarily aimed at young women.
This latest study, published in The Lancet, is based on tests carried out on 798 men between the ages of 16 and 25, who were undergoing basic army training.
They each agreed to have their urine screened for chlamydia as part of their routine medical examination.
White or cloudy, watery discharge from the tip of the penis
Pain or a burning sensation when passing urine
Testicular pain and/or swelling
The tests, which were carried out by Dr Gordon Scott and colleagues at Edinburgh Royal Infirmary, revealed that 78 men had been infected.
Sixty-nine of these men showed no signs of being infected. The remainder had minor symptoms but had not thought them serious enough to go a doctor.
The doctors said there was no evidence to suggest that these men were particularly at risk. On average, the recruits had had one sexual partner in the previous six months.
The doctors highlighted the high number of men who were infected without showing symptoms.
They said previous studies had shown that usually only 50% of those infected are asymptomatic or do not display symptoms.
They said these findings highlighted the need to screen young men for the infection.
"Our finding that the rate of asymptomatic infections was higher than that usually cited 50% shows the importance of involving men as well as women in opportunistic testing for chlamydia," they said.
The Department of Health in England said it was planning to screen young men for the infection as part of its national screening programme.
A spokesman said: "The programme will primarily target women under 25 who access sexual health services.
"Young women are the initial focus of screening as they attend health services more often than young men, suffer more from the long-term consequences and modelling suggests that this is a cost-effective approach.
"However, we will also be promoting greater uptake of testing amongst men."
The Scottish Executive has launched a series of pilot projects to identify the best way of encouraging young people to get tested for chlamydia.
This includes offering free home test kits in music stores in Lothian. Test results can be obtained through the post.
A spokeswoman for the executive said ministers were planning to evaluate the pilots later this year before deciding how best to tackle the rise in infections.