The purpose of this study was to investigate the utility of repeated applications of ceruletid to reduce gallbladder volume and its feasibility as a means of prophylaxis of acute acalculous cholecystitis in intensive care patients. First, a dose-response curve of ceruletid was obtained in 20 mechanically ventilated patients of a surgical intensive care unit (SICU) not receiving enteral nutrition. An effective dose of ceruletid, defined by a 50% reduction of gallbladder volume was established and subsequently studied in 40 mechanically ventilated SICU patients on total parenteral nutrition in a prospective, randomized, controlled, triple-blind trial. Gallbladder volume, sludge formation and side effects were evaluated. A dose of 1.5 micrograms/kg body weight ceruletid was established as the effective dose, causing 50% reduction of gallbladder volume in all patients studied and reduction of gallbladder sludge in 95%. In 67.5% of patients side effects were observed, requiring therapeutic intervention in 68%. It is concluded that ceruletid is effective in stimulating gallbladder contraction and reducing sludge formation in severely ill patients on intensive care units. Its routine use as prophylaxis of acute acalculous cholecystitis, however, may be limited by the nature, severity and frequency of side effects.