The mechanical behavior of rat skin during repeated strain in vivo and the restoration process thereafter were studied following 10 days’ treatment with desmotropic drugs (300 mg/kg p.o. D-penicillamine or 10 mg/kg s.c. prednisolone acetate). Repeated (30 times) elongations of up to 40% were performed under anesthesia both longitudinally and perpendicularly to the body axis. Evaluation of this first run of 30 cycles showed stress values as well as the moduli of elasticity to be decreased after D-penicillamine, whereas they were greatly increased after prednisolone acetate treatment. The decay of stress values during repeated strain revealed similar effects of treatment. In the second part of the experiment, the restoration process was evaluated by a second run of 30 cycles after 1, 6 and 16 h. In the late phases of recovery, an even better restitu-tio ad integrum was found in treated animals. Overall, in contrast to other biomechanical parameters, the restoration process is barely influenced by treatment with desmotropic compounds.