Background: To develop a nonsurgical treatment alternative for basal cell carcinomas (BCCs), we evaluated intralesional sustained-release chemotherapy with 5-fluorouracil/epinephrine injectable gel (5-FU/epi gel). Objective: To optimize the dose and treatment schedule, we compared the safety, tolerance, and efficacy of six treatment regimens of 5-FU/epi gel in patients with BCCs. Methods: Two doses and four treatment schedules of 5-FU/epi gel were compared in an open-label, randomized study of 122 patients with biopsy-proven BCCs. One BCC per patient was treated for up to 4 to 6 weeks, then observed for 3 months at which time the tumor site was completely excised for histologic examination. Results: Overall, 91% of evaluable treated tumors (106 of 116) in all regimens had histologically confirmed complete tumor resolution. No clinically significant treatment-related systemic adverse events occurred. The best response rate, tolerance, and patient compliance with assigned dose were in patients receiving 0.5 ml of 5-FU/epi gel three times a week for 2 weeks. The complete response rate based on histologic assessment in this group was 100%. Conclusion: Results demonstrate that treatment of BCC with 5-FU/epi gel is both safe and effective, may result in histologically confirmed complete response rates comparable to surgery, and provides a nonsurgical treatment alternative in selected patients. (J Am Acad Dermatol 1997;36:72-7.)