Extramammary Paget's disease (EP) has frequently underlying adnexal cancer and perhaps has a tendency to be associated with internal malignancies. Chanda (1985) reviewed 197 cases of EP (196 cases reported in the literature from 1962 to 1982 and 1 case of his own) with regard to the prognosis and relationship with internal malignancy. We analysed 68 cases of EP experienced in our clinic over the last 30 years and compared our data with Chanda's review. Of our 68 patients, 10 cases (14.7%) had an associated internal malignancy, while of Chanda's 153 patients, 44 (28.8%) had the same malignancy. Thirty-nine patients who had an associated internal malignancy have been reported in Japan including our 10 cases (1932-1986). In 25 Japanese cases occurring on the penis, scrotum or groin, the following internal malignant tumors were found, 3 each of prostatic and bladder cancer, 2 testicular malignancies (1 sarcoma and 1 malignant lymphoma), 1 hypernephroma and 16 other malignancies. In EP of the vulvar area, 2 each of uterine and bladder cancer, and 1 each of breast, colon and anal cancer were observed. In Chanda's data, the location of the associated internal malignancy appeared to be closely related to the location of the EP, i.e., a penile-scrotum-groin location being associated with male genitourinary malignancy, a vulva location being associated with female genitourinary malignancy and a perianal location being associated with adenocarcinoma of the digestive system. In the Japanese data, however, the associated internal malignancy was more widely distributed to other organs. Our data suggest that a more direct search should be made for internal malignancy in Japanese patients with EP than in Caucasians.