Fasting antral, duodenal, and jejunal motor activity and plasma motilin and pancreatic polypeptide were studied in 14 patients with systemic sclerosis, 6 and 9 without clinical evidence of small bowel involvement, and 8 healthy control subjects. Normal interdigestive motor activity was present in control subjects and patients without intestinal involvement. However, cyclic motor activity was absent in 3 of the patients with intestinal disease and the motility index per interdigestive cycle (or per 6-h recording period in those without cyclic activity) was significantly less in the antrum (181 +/- 103 mm2 compared with 760 +/- 86 and 1116 +/- 96 mm2 for patients without involvement and healthy control subjects, respectively), duodenum (153 +/- 101 mm2 compared with 1425 +2- 186 nd 1055 +/- 241 mm2), and jejunum (268 +/- 131 mm2 compared with 1166 +/- 97 and 1105 +/- 128 mm2). Metoclopramide and bethanechol significantly increased motor activity at the three sites in all subjects but the magnitude of the metoclopramide response was less in patients with intestinal involvement. Fasting concentrations of motilin and pancreatic polypeptide exhibited cyclic variation with peak values occurring during phase 3 of the interdigestive cycle. Plasma motilin during each phase of motor activity was significantly higher in patients with scleroderma, with or without intestinal involvement, than in control subjects. The abnormal motor activity demonstrated here indicates a possible mechanism by which intestinal stasis and bacterial overgrowth could occur and by which clinical disturbances of intestinal transit might arise.