OBJECTIVES: To determine the penile, perianal, and oropharyngeal candidal colonisation rates among homosexual and heterosexual males attending an STD clinic. To determine the prevalence of balanitis and candidal balanitis in the two groups. SUBJECTS: 252 heterosexual and 210 homosexual male patients attending consecutively the STD clinic in Coventry, England. DESIGN: A prospective study recording sexual behaviour, relevant history, symptoms, and examination. Specimens for candida culture were collected from the glans penis, perianal area, and oropharynx. RESULTS: Among the 462 men studied, penile, perianal, and oropharyngeal colonisation rates were 74 (16%), 70 (15%), and 116 (25%) respectively. On examination, 47 (10%) were found to have balanitis. Of the 74 patients with penile colonisation, 26 (37%) were symptomatic and 20 (27%) had balanitis. The 223 heterosexual and the 196 homosexual males who had sexual intercourse within 3 months had comparable colonisation rates of candida on the penis, perianal area, and oropharynx. Balanitis was seen in 31 heterosexuals (14%) and candidal balanitis in 16 (7%); the incidence was significantly less in homosexuals where balanitis was seen in 12 (6%) and candidal balanitis in four (2%). CONCLUSIONS: Itching or burning sensations after sex were the most common symptoms associated with penile colonisation with candida and were present in more than one third. Candidal balanitis was commoner in those who had vaginal than those who had anal intercourse within 3 months.