Nifedipine (10 mg), nisoldipine (10 mg) and nitrendipine (20 mg) were given orally to 8 normal volunteers in a placebo controlled, double blind, crossover study. Blood pressure (BP), pulse (P) and systolic time intervals (STI) were recorded at time 0, 30, 60, 90, 120 min after drug administration. Adverse effects were also recorded. There was a fall in BP, pre-ejection time (PEP), PEP/LVET (left ventricular ejection time) and electro-mechanical systole index (QS2 index), and a rise in LVET index in response to the three active drugs compared with placebo. All active drugs, but not placebo, were associated with adverse effects.