A prospective study of 65 men and 111 women with multiple heterosexual partners was designed to assess the prevalence and potential risk factors of genital human papillomavirus (HPV) infections. In addition, the HPV reservoir in genital, rectal, and oral mucosa was examined. The specimens for the detection of HPV DNA were taken from different sites such as the urethra and coronal sulcus (men), cervix and labia minora (women), anus, rectum, tongue, and buccal mucosa (both men and women). Women underwent speculum examination and colposcopic evaluation of the anogenital region, and a smear for routine cytological classification was also taken. In men, the anogenital region was examined clinically and colposcopically. The polymerase chain reaction (PCR) was used for the detection of HPV types 6/11, 16, 18, and 33. A high prevalence of HPV infection at one or more sites was detected, in 32% of the male and in 23% of the female participants. Seventeen percent of the male distal urethral specimens were positive for HPV DNA. From the female cervical specimens 14% were found positive. Ten proctal specimens (five men and five women) were positive for HPV DNA without any discernible lesion. The persons from whom these samples were taken denied anal insertive intercourse. No oral manifestation of HPV infection was detected. In both men and women a difference between HPV DNA-positive and -negative persons was not found in relation to known risk factors associated HPV infection.(ABSTRACT TRUNCATED AT 250 WORDS)