AbstractThe effects were studied of a methanolic extract of the brown alga Laminaria ochroleuca on the central nervous system (CNS) of mice. Spontaneous motor activity, exploratory behaviour, motor coordination, d‐amphetamine‐induced hypermotility, body temperature, pentobarbital‐induced hypnosis, pentylenetetrazole‐induced convulsions and analgesic activity were assessed. At doses between 25 and 100mg/kg, the extract showed significant activity in all tests except that of pentylenetetrazole‐induced convulsions. It is concluded that the methanolic extract of Laminaria ochroleuca is a CNS depressant with slight analgesic activity.