Primary anorexia nervosa (PAN) is an important psychiatric disease with a 7--21% mortality rate. Although altered gastrointestinal function may be an important aspect of its pathophysiology, no information is available concerning gastric emptying and secretion in those patients. During fasting, fractional emptying rates and hydrogen ion (H+) output were decreased twofold in PAN, as compared with healthy controls, and fluid output was slightly but not significantly decreased. Pentagastrin-induced peak stimulation of H+ output in PAN was 64% of that found in controls (P less than 0.05). Peak gastric fluid output was also significantly less in PAN patients, but suppression of fractional emptying produced by pentagastrin was of the same magnitude in both groups. Following a 250-ml water load, the magnitude and the duration of both the emptying and secretory responses were less in PAN patients than in controls. As a result, the initial increase of intragastric volume was greater in PAN patients than in controls, and the gradual return to fasting volume was delayed in those patients. Follow weight gain, fractional emptying tended to return toward control values, but was still significantly less than in controls following the water load. Gastric H+ and fluid output were not significantly modified following weight gain.