An analysis of lipids and histological examination were performed on tissues resected from 2 patients with sclerosing lipogranuloma of the scrotum. The clinical course and histological characteristics were consistent with those reported previously for typical primary sclerosing lipogranuloma of the male genitalia. There was no history of the injection or topical application of oils or fats. Both of our patients had eosinophilia and the lesions showed eosinophilic infiltration. Complete natural regression occurred several months after partial resection of the lesion in both cases, and no recurrence has been noted during follow-up. This lipid analysis and histological study revealed that no exogenous fatty elements were present and suggested that degeneration of endogenous fat due to some allergic mechanism might be involved in the development of sclerosing lipogranuloma. The eosinophilia associated with this disease and its spontaneous regression after partial resection also support this assumption.