Simultaneous recordings of gastric manometry and myoelectrical activity were made in 10 patients with gastroparesis. Intravenous erythromycin (100 mg) was administered in the fasting state for a period of 30 min. Subcutaneous injection of octreotide (100 microg) was administered before one of the four identical test meals. It was found that octreotide significantly decreased the antral motility index (30-min fasting: 4.51+/-1.04 vs 1.75+/-0.97, P < 0.02; 60-min fed: 5.16+/-1.44 vs 3.4+/-1.41, P < 0.05) and the dominant power of the EGG (fasting power: 35.19+/-1.54 vs 30.84+/-1.57 dB, P < 0.004; postprandial power increase: 5.52+/-1.06 vs -0.27+/-0.87, P < 0.001). Erythromycin significantly increased the antral motility index (3.16+/-0.96 vs 9.5+/-0.61, P < 0.001) and the dominant power of the EGG (28.86+/-1.57 dB vs 33.55+/-1.59 dB, P < 0.005) in the fasting state. An improvement in the regularity of the gastric slow wave was also noted with erythromycin. It was concluded that: (1) the inhibitory effect of octreotide on postprandial gastric motility and myoelectrical activity suggests that caution should be exercised when octreotide is used in patients with gastroparesis; and (2) the stimulatory effect of erythromycin on gastric myoelectrical activity may enhance gastric motility and gastric emptying in patients with gastroparesis.