In normotensive rats the effect of different doses of propranolol (1.0, 5.0 and 10.0 mg/kg i.p.) and ketanserin (10.0 mg/kg p.o.) on mean blood pressure and heart rate and on cardiovascular response to noradrenaline (0.1, 0.3, 0.5, 0.7 and 1.0 micrograms/kg i.v.) was examined. The drugs were given separately or together. Propranolol slightly reduced the hypotensive effect of ketanserin. On the other hand a decrease in heart rate caused by propranolol was not affected by ketanserin. Our results show that propranolol given with ketanserin did not change the effect of the latter on the cardiovascular system.