Sixty radiocarpal and midcarpal joints in 30 healthy adults and 20 swollen wrists in 20 patients with chronic arthritis were examined by dorsal longitudinal ultrasonography (US). In five other patients intraarticular application of fluid into the radiocarpal joint could be seen as a change in the US scan. In 49 out of the 60 healthy wrists the unechogenic zone dorsally above the scaphoid bone was less than two millimetres, and the measurement did not change in dorsal or volar flexion. The side difference was less than one millimetre. In the healthy wrists the midcarpal area above bones was echogenic in US. In 15 radiocarpal and in 10 midcarpal joints out of the 20 swollen wrists, effusion could be depicted with US as an unechogenic zone. It was two millimetres or more in radiocarpal joint and it got bigger in dorsal and smaller in volar flexion.