Long-term experiments on male rats revealed that better performers in the mating test are better learners in the shuttle box and the more active animals live significantly longer than their less active peers. It was established by the aid of (-)deprenyl, a highly specific chemical tool, which increases superoxide dismutase activity in the striatum, facilitates the activity of the nigrostriatal dopaminergic neurons with utmost selectivity, and protects these neurons from their age-related decay, that the efficiency of a male rat in behavioral tests, as well as the duration of its life are striatal dopamine dependent functions. As a measure of striatal function, sexual activity was tested once a week in a group of male rats (n = 132) from the 24th month of their life. Because of the age-related decay of this function none of the 2-year-old animals displayed full scale sexual activity. By dividing the group equally the rats were treated with saline (1 ml/kg, s.c.) and deprenyl (0.25 mg/kg, s.c.), respectively, three times a week. In the saline-treated group (n = 66) the last signs of sexual activity vanished to the 33rd week of treatment. (-)Deprenyl treatment restored full scale sexual activity in 64 out of 66 rats. The longest living rat in the saline-treated group lived 164 weeks. The average lifespan of the group was 147.05 +/- 0.56 weeks. The shortest living animal in the (-)deprenyl-treated group lived 171 weeks and the longest living rat died during the 226th week of its life. The average lifespan was 197.98 +/- 2.36 weeks, i.e. higher than the estimated maximum age of death in the rat (182 weeks). This is the first instance that by the aid of a well-aimed medication members of a species lived beyond the known lifespan maximum.