About 5% of the heavy abdominal traumas present a traumatic diaphragm rupture (14). A correct diagnosis of such a rupture is usually not obvious. A collective review by Alivisatos concluded that only 1/3 of the diaphragm ruptures was recognized within the first 24 hours (2). In the department of general surgery of the academic hospitals St-Raphaël and St-Pieter, 38 cases were seen during the last ten years (1970-1980). The diagnosis was made within the first 24 hours (pre- or peroperatively) in 28 cases. In 34 cases, diagnosis was achieved within a week of time and in 36 cases within a year. In only 2 of the cases it was achieved after 1 years time. In this paper two points are especially emphasized, first why a correct diagnosis sometimes is so difficult to reach and second which dangers can result from an unseen diaphragm tear. These points of interest are illustrated by a few remarkables case.