While a great deal of attention has been paid to the effect of erythromycin (Ery) on gastric contractility, its effect on gastric myoelectrical activity, which controls gastric motility, remains unknown. In this study, Ery (6 mg/kg) was infused intravenously in 14 normal human subjects (placebo controlled). Gastric myoelectrical activity was recorded using the surface electrogastrographic method. The electrogastrogram (EGG) recordings were analyzed using spectral analysis methods. It was found that the presence of the 2-4 cycles/min activity (normal slow wave frequency range) in the EGG was 51 +/- 19% in the first hour of the intravenous Ery infusion, which was significantly smaller (P less than 0.001, t test) than that (72 +/- 20%) during the corresponding control period (intravenous saline). This difference was, however, not quite significant (P = 0.067, t test) in the second hour after the infusions. The average score for nausea during Ery was 4.5 (0 for no nausea, 10 for the most severe nausea). We conclude that 1) intravenous Ery induces irregularities in the cutaneous EGG in normal human subjects; and 2) the noninvasive cutaneous EGG is an attractive method both for the investigation of the effects of pharmacological and prokinetic agents such as Ery on gastric myoelectrical activity in humans and for correlating clinical responses to changes in the EGG.