The bronchodilator activity of an aqueous fraction (AF) of a 70% hydroalcoholic extract of the leaves of Cissampelos sympodialis Eichl. was evaluated in the guinea-pig. The AF inhibited the spontaneous tone of the trachea (IC(50), 13.9 μg/ml), which was potentiated (IC(50), 4.6 μg/ml) by