We report the effects on the central nervous system (CNS) and on analgesic activity of a fraction (F2) obtained from a Himanthalia elongata extract. The fraction was assayed for effects on spontaneous locomotor activity, d-amphetamine-induced hypermotility, motor coordination, muscular relaxation, rectal temperature, sodium pentobarbital-induced hypnosis, and pentylenetetrazole-induced convulsions. Analgesic activity was evaluated using the hot plate test and the Randall-Selitto test (1). The fraction caused significant reductions in spontaneous locomotor activity, hypermotility, rectal temperature, and motor coordination and postponed pentylenetetrazole-induced death, but no effect was noted on muscle relaxation or the duration of sodium pentobarbital-induced sleep. The fraction exhibited central analgesic effects in the hot plate and Randall-Selitto tests.