1. In patients with cystic fibrosis, abnormalities in plasma cholecystokinin level and gall-bladder emptying may contribute to the development of maldigestion and gall-stones.

2. Therefore, we have measured plasma cholecystokinin levels and gall-bladder volumes before and after ingestion of a standard breakfast in eight adult patients with cystic fibrosis and in eight normal control subjects.

3. In the patients with cystic fibrosis basal (2.8 ± 0.4 pmol/l; P < 0.05, t-test) and maximum post-prandial (5.7 ± 0.5 pmol/l; P < 0.05, t-test) plasma cholecystokinin levels were significantly higher than those in the control subjects (1.9 ± 0.1 pmol/l, and 4.5 ± 0.2 pmol/l, respectively). On the other hand, integrated plasma cholecystokinin secretion in response to the meal was similar (t-test, P = 0.4 versus control subjects). The increased plasma cholecystokinin levels in the patients with cystic fibrosis were accompanied by reduced gallbladder volumes in both the basal (7.8 ± 2.1 cm³ versus 20.9 ± 2.3 cm³ in control subjects; P < 0.005, t-test) and the post-prandial state (2.2 ± 1.0 cm³ versus 4.8 ± 0.8 cm³ in control subjects; P = 0.06, t-test). Gall-bladder emptying in the patients with cystic fibrosis was well preserved (70 ± 7% versus 78 ± 9% in control subjects; P = 0.4, t-test).

4. In comparison with normal control subjects, patients with cystic fibrosis have an increased basal plasma cholecystokinin level and a reduced gall-bladder volume, whereas post-prandial gall-bladder emptying and plasma cholecystokinin secretion are not significantly different. In cystic fibrosis, neither impaired cholecystokinin release nor impaired gall-bladder emptying appear to play a role in the pathogenesis of either gall-stones or maldigestion.