The objective of this thesis was to investigate various aspects of the epidemiology of human papillomavirus (HPV). Prospective studies were performed on a total of 334 patients attending to genitourinary medicine departments in London. The patients had either clinical indications for genital biopsy, urethral gonorrhoea, anogenital warts or a current partner with anogenital warts. Biopsy, scrape, swab and blood samples were taken. In addition, a new method, the "Superglue (SG) technique" was devised. HPV types 6, 11, 16, 18, 31 and 33 were identified in the specimens by DNA extraction followed by the polymerase chain reaction, Southern blotting and hybridisation. HPV DNA was detected in 31.8 to 96.6% of biopsies with histological evidence of wart virus infection, 83.3% of biopsies with neoplasia and 18.2% of those with other histological changes. HPV DNA was detected in 31.3 to 61.1% of urethral loop specimens, 18.0 to 24.8% of urethral swab specimens, 6.3 to 12.5% of urine specimens, 37.5% of vaginal washes and 21.4% of rectal swab specimens. Fifty percent of samples obtained with the SG technique containing human cells had detectable HPV DNA. HPV types 6 and 11 tended to be found in biopsies from lesions clinically associated with HPV infection and in the urethras of men with warts seen near the urinary meatus. HPV types 16 and 18 tended to be found in specimens obtained by techniques other than the biopsy method and from clinically atypical lesions. Infections with multiple HPV types were common. Different sites from one patient sometimes had HPV types in common.