Although human immunodeficiency virus (HIV) rates are increasing rapidly in Asia, a full understanding of the extent of other sexually transmitted diseases (STDs) in many of these areas is lacking. There have been anecdotes of rising rates of STDs in Mongolia, a country thus far relatively unaffected by HIV. To further the understanding of STDs, a prevalence study was conducted in the STD clinic in Ulaanbaatar, the capital and largest city in Mongolia. Among 260 patients, the prevalence of gonorrhoea, chlamydia and syphilis was 31.1%, 8.1% and 8.6% respectively for males and 10.3%, 9.9% and 6.0% for females. Sixty-seven per cent of females had trichomoniasis and 19.7% of males had non-gonococcal urethritis (NGU). Forty-two per cent of gonococcal isolates had plasmid mediated resistance to penicillin, and chromosomal resistance to penicillin, tetracycline, and ciprofloxacin was documented. No patients were infected with HIV. STDs are a significant problem in Mongolia. Improved control efforts are urgently needed to prevent the emergence of HIV.