Immunosuppressed patients such as transplant recipients are known to develop multiple lesions suggestive of human papillomavirus (HPV) infection. A giant anal condyloma was obtained from a transplant patient; several fragments taken from different areas were examined for the presence of HPV DNA using in situ hybridisation, polymerase chain reaction (PCR) and Southern blot. Typical koilocytes were seen in routinely stained tissue sections, suggesting an HPV infection; furthermore, group specific HPV antigen was detected in one of four frozen fragments. Different results were obtained by in situ hybridisation according to the fragment tested. HPV types 6/11 were detected in each of the five fragments, frozen or fixed in Bouin's or formalin solutions. However, the number of HPV DNA positive cells and the intensity of the reaction greatly varied with the specimen. HPV 16 and 18 probes also reacted positively with the sample fixed in formalin; a stronger signal was observed with HPV 18 in one large focus than with HPV 16. HPV type 5 was detected in a few isolated cells of two frozen fragments. With the Southern blot technique, the profile of an HPV 6/11 was seen only in one of two frozen fragments; in this case, the bands were intense. A slight positive reaction was also obtained in one frozen fragment with HPV 16 probe. Four frozen fragments were analyzed with PCR: HPV 6/11 was detected in each fragment; HPV 18 was detected in the four samples but with different intensities; HPV types 5 and 16 did not show any positive signal. In conclusion, the lesion is an example of infection with several HPV types, demonstrated by three different techniques. This suggests the need for careful dermatological or colposcopic follow-up of transplant recipients, in order to prevent possible malignant transformation of anogenital lesions.