Objective: To investigate gallbladder function by use of cholescintigraphy in patients with acute cholecystitis before and after percutaneous gallbladder drainage. Design: A cholescintigraphy was performed in 40 patients with acute cholecystitis before and after the performance of percutaneous gallbladder drainage. During the post-drainage cholescintigraphies, a cholecystokinin stimulation was performed to investigate gallbladder emptying in 12 selected patients. Gallbladder pressure and volume were measured before drainage in another group of 12 patients with acute cholecystitis. Results: As expected, no gallbladder activity was observed in the cholescintigraphies before drainage, except in a patient with an occluding stone in the common bile duct. Cystic duct patency and gallbladder activity were seen in 80% of patients in cholescintigraphies performed after drainage but before any other treatment. Post-drainage cholescintigraphy revealed a mean gallbladder ejection fraction of 24%, which is significantly lower than the corresponding value in normal individuals and gallstone patients without cholecystitis (n=12). Gallbladder pressure and volume were markedly increased compared with normal values. Conclusion: The relief of increased gallbladder pressure and volume appears to be important for the re-establishment of gallbladder function.