Leaves of Maytenus species are used in the popular medicine of Brazil for their reported antacid and antiulcerogenic activity. The present work examined the effects of a boiling water extract of equal parts of M. aquifolium and M. ilicifolia leaves on acute administration in rats and mice, in an attempt to detect any general depressant, hypnotic, anticonvulsant and analgesic effects. General depressant and hypnotic effects were seen only after intraperitoneal administration. After chronic administration, the overall behavior of animals did not change and they continued to gain weight at the same rate as controls. Several biochemical and hematological parameters as well as pathological examination of different organs did not show any significant alterations after 3 months of treatment. A search for the potential effects of the extract on the fertility of female and male rats and on the course of pregnancy as well as a search for potential teratogenic effects did not reveal any significant differences from controls. Taken together, the results indicate that these Maytenus species may be safe for human use and deserve further investigation.