The inter-rater reliability of the Injury Severity Score (ISS) and the Polytraumaschlüssel (PTS) [multiple trauma code] was studied using diagnosis sheets filled in for 107 multiple injured patients. The scoring was performed by eight physicians with different levels of qualification. The scores for individual patients varied widely depending on the scorer, with extremes differing from the mean by about 80% and 70% for the ISS and PTS, respectively. The mean ISS and PTS for the whole study population also varied significantly between the scorers (P less than 0.0001, one-way analysis of variance). Raters with experience in trauma scoring calculated significantly higher scores (P less than 0.01, t-test) Neither the ISS nor the PTS seem reliable enough to describe injury severity in an individual patient. Treatment decisions must not be based on such grounds. Even for larger groups, caution must be exercised in comparison of different populations of multiple traumatized patients.