We studied eighty-nine nodular hidradenomas (NHs) and six clear cell hidradenocarcinomas (CCHs) reported in a 10-year period. NHs were more commonly seen in women (ratio of 1.7 to 1); the average age was 37.2 years, and they were located mainly on the head. One CCH had widely disseminated metastasis that led to death. Other CCHs underwent spontaneous regression.