The role of central alpha 2-adrenoceptors in male sexual behaviour was investigated by administering the selective agonist, guanabenz, and the selective antagonist, efaroxan, to both sexually experienced and sexually inexperienced male rats. In sexually experienced animals, guanabenz, at the dose of 1 mg/kg i.p., increased mount and intromission latencies (ML, IL), intercopulatory interval (ICI) and post-ejaculation interval (PEI), and reduced mount and intromission frequencies (MF, IF) and copulatory efficacy (CE). Efaroxan, at the dose of 10 mg/kg i.p., reduced ML and IL. In sexually inexperienced animals, guanabenz, at the dose of 1 mg/kg i.p., slightly reduced the percent of animals achieving ejaculation and increased PEI. Efaroxan, either at the dose of 3 or 10 mg/kg i.p., increased the percent of animals achieving ejaculation and--only at the dose of 10 mg/kg i.p.--reduced EL. Finally, in sexually experienced animals, efaroxan (10 mg/kg i.p.) prevented the effect of guanabenz (1 mg/kg i.p.). On the whole, these data further indicate that, in rats, male sexual behaviour is positively modulated by brain noradrenergic systems.