The central nervous system (CNS) depressant and anticonvulsant activities of the aqueous root extract of Sanseviera liberica (ASL) were investigated on various animal models including pentobarbitone sleeping time and hole-board exploratory behaviour for sedation tests, and strychnine, picrotoxin, bicuculline and pentylenetetrazole-induced convulsions in mice. ASL (100-400mg/kg, p.o.), like chlorpromazine HCl (1mg/kg, i.m.), produced a dose-dependent prolongation of pentobarbitone sleeping time and suppression of exploratory behaviour. ASL (100 and 200mg/kg) produced dose-dependent and significant (P<0.05) increases in onset to clonic and tonic convulsions, and at 400mg/kg, showed complete protection against seizures induced by strychnine, picrotoxin and bicuculline, but not with pentylenetetrazole. ASL up to 10 g/kg, p.o. did not produce death, but i.p. treatment produced mortalities with LD(50) of 668.3+/-47.6 mg/kg. Preliminary phytochemical investigations of ASL revealed the presence of carbohydrates, alkaloids, saponins, reducing sugars and oils. The results indicate that ASL has sedative and anticonvulsant activities, therefore, justifying its use in traditional African medicine.