In a randomized double-blind controlled study, 19 patients applied 5% 5-fluorouracil (5-FU) cream to actinic keratoses (AK) on each arm twice daily, followed by nightly application of 0.05% tretinoin cream to one arm, and a control cream to the other arm until discomfort precluded further applications. After 3 months, the number of residual AK was compared to pre-treatment values. The tretinoin-treated arms had 15.7 +/- 6.1 AK before treatment and 3.4 +/- 2.6 AK following therapy. The control arms had 15.3 +/- 6.9 AK before therapy and 4.2 +/- 2.5 lesions afterwards. Using a one-tailed paired t-test, the difference in response was statistically significant (0.03 less than P less than 0.04). It was concluded that daily application of 0.05% tretinoin cream appeared to enhance the efficacy of topical 5-FU in destruction of AK of the arms and may represent a useful treatment modality.