Diuretic activity of five medicinal plants (Cassia alata L., Zanthoxylum fagara L., Nectandra coriacea Sw, Costus pictus D. Don, and Persea americana Miller) used by Cuban population was assessed. Plants decoctions (30 %) were applied to Wistar male rats (400 mg/kg BW), based on total solids and completed with physiological saline solution up to a total constant administration volume of 40 ml/kg BW and administered to 7 experimental groups: 5 treated, a positive control (furosemide, 20 mg/kg) and a negative control (NaCl, 0,9 %). Animals were placed in metabolic cages, decoctions administered and urinary excretion quantified after ½, 1, 2, 3, 4, 5 and 6 h. After the urinary excretion, diuretic action and diuretic activity were calculated. Urine volumes were increased in all treated groups when compared to negative control, being superior in C. alata and P. americana and, at the same time, similar to the reference diuretic used.Colegio de Farmacéuticos de la Provincia de Buenos Aires