Sonograms of 412 consecutive patients with operatively and histologically proven acute or chronic cholecystitis were reviewed retrospectively. 267 of them had been operated on in an acute phase of gallbladder disease and 145 had undergone an elective operation. 236 patients had an operative and/or histological diagnosis of acute cholecystitis and 176 both operatively and histologically confirmed chronic cholecystitis. A thickened gallbladder wall was seen in 80% of acute cases, wall sonolucency in 39%, dilated gallbladder in 60%, sludge in 26% and stones in 75%, the corresponding proportions of the chronic cases being 18%, 4%, 12%, 13% and 93%. A contracted gallbladder with stones was seen in 15% of the chronic and 1% of the acute cholecystitis cases. 90% of the acute cases had two or more sonographic abnormalities, whereas 70% of the chronic cases had only one abnormality, most frequently gallstones. Only one normal sonographic finding was recorded in each group.