Dose-response curves for proliferating, nonproliferating, and nonproliferating hair coat stimulated 24 hours after treatment show similar Dq of 135 rad and a Dq of 500, 900, and 1400 rad respectively. Using a priming dose of 650 rad X-rays, a drug-dose-response curve was established in the proliferating hair coat. Drugdose-response curve was established for the nonproliferating, stimulated coat with priming doses of 1200 and 1400 rad. No drug effect could be seen in the nonproliferating hair coat left unstimulated. Cyclic interaction between drug and irradiation was found in the proliferating hair coat. © 1979.