During a 6-year period 22 patients were operated on because of iatrogenic arterial trauma (group A) and 43 sustained noniatrogenic arterial injury (group B). The group A injuries were caused by various arterial catheterization procedures for angiography or cardiac investigation (55%) or surgical interventions (45%). Haemorrhage was more common in group B than in group A (p less than 0.001). The mortality rate did not differ significantly between the groups (14% vs. 9%). Permanent disability was more common in group B (p less than 0.05), due mainly to higher incidence of associated venous, neural, skeletal or visceral injuries. Bypass operations tended to be more often performed in group B than in group A, but the difference was not statistically significant. Retrospective assessment of the appropriateness of technique, made separately by two vascular surgeons, revealed instances of potentially avoidable iatrogenic arterial injury. The rising incidence of iatrogenic arterial trauma may therefore be considered 'reducible'.