Gastric emptying of a solid meal and of 10 indigestible radiopaque solids was measured with scintigraphic and radiological techniques in 50 healthy volunteers (controls), 41 patients with insulin-dependent diabetes mellitus, and 50 patients with functional dyspepsia. Gastroparesis was found in 51% of our diabetic patients and 74% of our patients with dyspepsia. The values of T-lag, T-1/2 and the percentage of isotope remaining in the stomach at 3.05 min were 14.9 min, 59.4 min and 25.3% in control subjects; 21.4 min, 88.1 min, and 46.9% in diabetic patients (P < 0.05 vs the control group); and 23.2 min, 114.6 min, and 58.7% in dyspeptic patients (P < 0.05 vs the control group). Whereas all healthy volunteers emptied all 10 indigestible solids in less than 4 hr, only 51% and 32% of diabetics and dyspeptics, respectively, achieved this emptying time (P < 0.01). Their respective values of T-1/2 were 81 min, 212 min, and 203 min (P < 0.01 for; diabetics and dyspeptics vs controls). We found no correlation between the findings for gastric emptying of digestible and indigestible solids. We conclude that gastroparesis affecting digestive and interdigestive motility is present in a high percentage of diabetics and functional dyspeptics and that conscientious evaluation of gastroparesis in both groups requires studies designed specifically to characterize each type of motility.