Background: Because of the uncommon nature of dermal spindle cell tumors, the effectiveness of various treatment modalities is difficult to assess. Objective: Our purpose was to measure the effectiveness of treating dermatofibrosarcoma protuberans, atypical fibroxanthoma, malignant fibrous histiocytoma, and leiomyosarcoma by means of Mohs micrographic surgery (MMS). In addition, we attempted to determine whether MMS is useful in treating dermal spindle cell tumors when no definitive histopathologic diagnosis can be rendered. Methods: In a retrospective chart review, demographic data, tumor data, treatment characteristics, recurrence, and follow-up data were tabulated. Results: The recurrence rate for dermatofibrosarcoma protuberans treated by MMS was 3.0%, for atypical fibroxanthoma was 6.9%, for malignant fibrous histiocytoma was 43%, and for leiomyosarcoma was 14%. The recurrence rate for spindle cell tumors not otherwise specified was 0%. Conclusion: These data establish the effectiveness of MMS in the treatment of dermal spindle cell tumors, including those for which no definitive histopathologic diagnosis can be rendered. (J Am Acad Dermatol 2001;44:656-9.)