β₂-Adrenoceptor agonists possess antidepressant-like activity in animals and man, but their peripheral side-effects prevent their therapeutic use. Atypical β-adrenoceptors have not been demonstrated in the central nervous system, but are known to exist in peripheral tissues such as the rat colon. We have now studied the antidepressant-like effects in rodents of a new selective atypical β-adrenoceptor agonist, SR 58611A. SR 58611A was active with minimal effective doses of 0.1–0.3 mg kg⁻¹ i.p. in several models (antagonism of the hypothemia induced by apomorphine and reserpine; potentiation of the toxicity produced by yohimbine; reversal of learned helplessness), but was inactive in the test reserpine-induced ptosis and behavioural despair. The antidepressant-like effect of SR 58611A was not antagonised by selective β₁- or β₂-adrenoceptor antogonist, but was blocked by high doses of the non-selective β-adrenoceptor antagonists, propranolol and alprenolol. Unlike β₂-adrenoceptor agonists, SR 58611A did not reduce locomotor activity or increase water intake at doses up to 10 mg kg⁻¹. Therefore, SR 58611A may represent the prototype of a new class of antidepressant compounds.