In this study, different extracts, fractions and subfractions from the seeds of Syzygium cuminii Linn. Skeels, have been evaluated for behavioural effects in mice, particularly in relation to their sedative and anticonvulsant actions. Oral treatment with the hydroalcoholic extract showed an anticonvulsant activity in pentylenetetrazol-and maximal electroshock-induced convulsions, besides a hypothermic effect. The infusion, the aqueous and ethyl acetate fractions of the hydroalcoholic extract, as well as the subfractions of the latter subfraction, promoted a decrease in spontaneous activity of mice after i.p. but not after p.o. treatment. The ethyl acetate fraction and its subfractions enhanced latency and duration of the first convulsion induced by pentylenetetrazol. One of the subfractions of the ethyl acetate fraction, a mixture of about five polyphenolic compounds, whose main constituent is gallic acid, also presented a depressant profile without an anticonvulsant activity. Our results suggest that S. cuminii has some active principles with central depressant properties, and some of them also present an anticonvulsant action, although the polyphenolic compounds do not seem be the main constitutents responsible for this effect.