A study was made of iatrogenic complications (IC) occurring in the department of cardiology of the Nantes Teaching Hospital Group between May 31, 1990 and June 1, 1991. One hundred and fifty eight IC were seen during this period, i.e. an annual incidence of 4.4%. There were 4 deaths following and IC, i.e. an annual mortality rate of 0.11%. Five other IC had serious though non-fatal consequences. Taken in general, IC appeared to be benign and of various origins. Drugs were responsible for almost half of IC and invasive investigations for one third. Application of a simple and single preventive approach is difficult in view of the diversity of causes. The solution lies in part in awareness and education concerning the problem, in which a permanent register system like ours certainly has a role to play.