"Juvenile" adenofibromas that presented in 25 patients were reviewed. All of the patients were in the second decade of life. The tumors were solitary in 19 patients and multiple and bilateral in six patients. All were distinguished microscopically by prominent cellularity of both epithelium and stroma. Patients who presented with solitary tumors, regardless of size, microscopic pattern, or manner of excision, had no recurrence. In contrast, all patients who presented with multiple tumors developed additional benign masses, often requiring re-excision. We believe that solitary "juvenile adenofibromas," regardless of size, should be excised so as to preserve as much breast tissue as possible. Those patients with multiple, bilateral tumors may anticipate recurrences, but malignant change is not seen. Tumors with this microscopic pattern also may occur, albeit uncommonly, in adults.