The goal of the present work was to characterise the effects of selegiline on the rat sleep pattern. Furthermore, for comparative purposes, the pharmacokinetics of selegiline and its metabolites in brain and plasma were investigated, and microdialysis experiments were performed to examine the resulting effect on dopamine, noradrenaline and serotonin levels. Selegiline (1, 5, 10 and 30 mg/kg) was found to dose-dependently increase the time spent awake following acute dosing. The pharmacokinetic assessment of selegiline showed that, following an oral dose of 5 mg/kg, low circulating levels of the parent compound were found relative to those of biotransformed l-methamphetamine and l-amphetamine. The time course of selegiline-induced wakefulness was shown to follow the time course of l-methamphetamine and l-amphetamine in brain, suggesting that these metabolites are responsible for the modulation of sleep architecture. Furthermore, selegiline (5 mg/kg) caused a significant increase of extracellular levels of DA (250%) and NA (200%), but not of 5-HT, in the rat prefrontal cortex. In summary, an integrated experimental approach was undertaken here to evaluate selegiline's effect on sleep architecture in rats in relation to its pharmacokinetics and changes in monoaminergic neurotransmitter levels in the brain. The effect of selegiline on sleep was likely mediated by an increase of dopamine and noradrenaline levels in the brain caused by the formed metabolites.