Background: Pilomatricomas have a wide variety of clinical characteristics and are often misdiagnosed. This can result in extensive surgery for an essentially benign condition. Objective: The purpose of this study was to define the clinical and histologic spectrum of these tumors to aid diagnosis. Methods: Two hundred nine cases were analyzed retrospectively with regard to age at presentation, site, size, and physical appearance. Results: Pilomatricomas appear at any age, with peak presentation bimodally in the first and sixth decade. Their most common site is the head and neck. Presentation is of a hard nodule, either deeply subcutaneous and invisible or superficial with possible erosion through the skin surface. This may lead to a false diagnosis of malignancy or of an epidermoid cyst. An association with myotonic dystrophy has been confirmed, as is the rare occurrence of malignant transformation. Conclusion: Careful clinical examination and a high index of suspicion results in an accurate diagnosis, appropriate treatment, and the avoidance of unnecessarily extensive surgery. (J Am Acad Dermatol 1998;39:191-5.)