The EEGraphic, behavioural and autonomic changes induced by the administration of some inhibitors of serotonin (5-HT) reuptake were evaluated in the rabbit. The drugs examined were: Alaproclate (Ala), Citalopram (Cit), Fluoxetine (Fluo), Fluvoxamine (Fluvo), Indalpine (Ind), Zimelidine (Zim). It seems that all these drugs would act exclusively or prevalently on 5-HT uptake. The changes of the parameters studied were not homogeneous. Some of these drugs (Cit, Zim) induced an EEGraphic and behavioural "arousal" pattern, others (Fluo, Fluvo) a "slow wave sleep" one, others (Ala, Ind) a biphasic one (alteration of the two above-mentioned patterns). The possible hypotheses subtending these data are discussed.