OBJECTIVES: I. Compare the rate of new skin cancer in patients with previously treated stage 0, I, or II basal or squamous cell skin cancer treated with eflornithine (DFMO) vs placebo. II. Determine whether inhibition of TPA-induced ornithine decarboxylase activity serves as an intermediary marker for response to DFMO in these patients. III. Determine whether inhibition of skin polyamine levels serves as an intermediary marker for response to DFMO in these patients. IV. Assess the long term toxic effects of this treatment in these patients.