Gastric emptying was evaluated in 15 children (mean age, 8.0 years) with progressive muscular dystrophy to detect early gastrointestinal smooth muscle involvement; 10 of the children also underwent esophageal manometry. Clinical evidence of skeletal muscle dysfunction was minimal in 14 of the 15 patients; 10 of them had no gastrointestinal symptoms. Gastric emptying studies were performed by using 500 muCi of technetium 99m-sulfur colloid bound to a scrambled egg, and scintigraphic measurements were made continuously for 60 to 90 minutes. Gastric emptying studies and manometric tracings were compared with those from 11 children (mean age, 8.4 years) without gastrointestinal or muscular disorders. Mean (+/- SD) percentage retention of gastric isotope was significantly greater in patients with muscular dystrophy than in control subjects. No differences were found between the two groups in distal esophageal motility or in upper and lower esophageal sphincter pressures or relaxation. Contraction amplitudes in the upper portion of the esophagus, however, were significantly lower in patients with myopathy than in control subjects. These data suggest that dysfunction of smooth muscle of the upper gastrointestinal tract is detectable in children with muscular dystrophy early in the course of the disease, even when gastrointestinal symptoms are absent and skeletal muscle symptoms are minimal.