The monoamine-oxidase-B (MAO-B) inhibitor l-deprenyl (selegiline) is effective in treating Parkinson's disease and possibly cognitive deficits associated with aging, Alzheimer's disease and HIV dementia. The aim of the present study was to investigate the effects of l-deprenyl on short- and long-term recognition memory in aged rats. Young adult and aged male Wistar rats were trained in a novel object recognition task. Retention test trials were carried out at 1.5 or 24 h after training. Aged rats showed impaired recognition memory retention 24 h after training when compared to young animals. Treatment with a daily systemic injection of l-deprenyl (1.0 mg/kg) for 21 days reversed the memory impairment. A control experiment indicated that l-deprenyl did not affect sensorimotor functions. The results suggest that l-deprenyl reverses age-related deficits in long-term recognition memory.