We have compared the ability of nifedipine and lacidipine, a new 1,4-dihydropyridine, to interfere with postprandial gastrointestinal motility. Five conscious dogs, fitted with 8 bipolar electrodes along the gastrointestinal tract, were studied. Gastrointestinal spike activity was evaluated by means of a computer system. Lacidipine (8 micrograms kg-1) was administered as an i.v. bolus immediately followed by a 10 micrograms kg-1 h-1 i.v. infusion for 3 h, starting 30 min before a standard meal. This dose of lacidipine decreased systolic blood pressure by approximately 20%. Nifedipine was used at equihypotensive doses (30 micrograms kg-1 i.v. bolus followed by 300 micrograms kg-1 h-1 i.v. infusion). Lacidipine had no effect on either gastric or intestinal postprandial spike activity. Nifedipine significantly delayed the appearance of the fed pattern and reduced the number of spikes in the small bowel, while it had no effect on gastric spike activity. We conclude that equihypotensive doses of lacidipine and nifedipine differ in their effects on the gastrointestinal tract, lacidipine having a better cardiovascular selectivity profile than nifedipine, and that the sensitivity to nifedipine varies in different parts of the gut.