The effects of an ethanol extract of the aerial parts of Ruta chalepensis on the central nervous system (CNS) and LD(50) determination were studied in mice. A crude extract was given systemically and its effects were tested on pentylenetetrazole (PTZ)-induced seizures, sodium pentobarbital-induced hypnosis, exploratory activity, anxiety and nociception. Results from the experimental models tested showed: (1) a delay in the onset of seizures and a dose-dependent suppression in the tonic phase and mortality induced by PTZ; (2) a prolongation of the time of sodium pentobarbital-induced hypnosis; (3) a significant attenuation in the anxiety-response and (4) a reduction in the licking time and shaking behavior in the formalin-induced nociception test. The sedative-hypnotic potentiation, anxiolytic, anticonvulsant and antinociceptive effects suggest that Ruta chalepensis induces a depressant activity on the CNS.