Plasma cholecystokinin (CCK) levels were measured by radioimmunoassay in 100 children (mean age: 20 months) on various types of artificial nutrition. Of the 81 children given total parenteral nutrition (TPN), 32 were studied while on cyclic TPN (cTPN), 66 while on partial fractioned feeding completed by parenteral nutrition, 25 while on constant rate enteral nutrition, and 18 while on total discontinuous oral feeding. The remaining 19 control cases were on normal alimentation. Plasma CCK levels during TPN (21.4 +/- 1.6 pg/ml), cTPN (21.8 +/- 2.7 pg/ml), and constant rate enteral nutrition (26.4 +/- 2.8 pg/ml) were not significantly different from each other and were similar to preprandial total discontinuous feeding (21 +/- 2 pg/ml) and control (22.6 +/- 3.5 pg/ml) levels. The postprandial CCK level increased significantly in partial fractionated feeding (33.6 +/- 3.3 pg/ml, p less than 0.02) but remained half that of postprandial total discontinuous oral feeding (75.6 +/- 6.6 pg/ml, p less than 0.001) and postprandial controls (75 +/- 7 pg/ml, p less than 0.001). Thus, basal and stimulated CCK levels are similar in children and adults, and the use of long-term artificial nutritional techniques does not modify the feeding stimulation of CCK. Plasma CCK levels during TPN and constant rate enteral nutrition are similar to fasting values, indicating a possible role for CCK in the biliary sludge.