Fifty seven patients (51 women and 6 men) undergoing cholecystectomy had ultra-sound evaluation on the 3rd, 5th, 7th and 9th post-operative days. In all the cases, the right upper quadrant has been observed correctly with a phased array 3.5 MHg transducer. Eleven of the fifty seven patients (19%) were found to have fluid collection in the gallbladder fossa. The collection has a rounded or an oval configuration, in the proportion of 11 and 55 mm, surrounded by an echogenic area. These fluid collections were of no clinical and biological significance and disappeared in 2 or 4 days time. The authors discuss the relationship between the presence of fluid and the use of drains or different surgical techniques.