The MAO-B inhibitor selegiline is used in the treatment of Parkinson's disease. Further, beneficial effects in Alzheimer's disease have also been described as well as neuroprotective effects, increased longevity and an attenuation of age-related cognitive decline in experiments using rats. Our studies in mice and Syrian hamsters aim at the question whether the effects of selegiline reported in the rat can be generalized to other species. Aged female NMRI-mice (23 mo.) treated with selegiline (0.25 mg/kg, i.p., 3 times a week for 2-3 weeks) showed no treatment effect in the Morris water maze and in passive avoidance learning after 2 and 3 weeks of treatment. However, Syrian hamsters chronically treated with selegiline (0.05 mg/kg/day in the food, starting at 12 months old) showed a 3 month delay in the age-related decline of spontaneous alteration behavior, a measure of longer-term memory, compared to untreated controls. Since treated hamsters also show increased longevity (study still in progress) the data suggest a protective effect of a chronic treatment with selegiline against age-related cognitive and physical decline.