Interferon-alpha is currently prescribed for many viral and neoplastic diseases; however, its side effects are poorly known. In this study, cardiovascular manifestations were specifically evaluated in 138 patients given interferon-alpha 2a for various dermatological diseases between 1987 and 1990. These patients were subjected to an indepth cardiovascular examination before the initiation of therapy and were monitored regularly throughout the treatment period. Six cardiac manifestations (4.3%) were observed, among which one unreported complete atrioventricular block. These side effects occurred at low doses (3-12 x 10(6) IU) in patients whose mean age was 63 years; 5 of the 6 patients had had previous cardiovascular incidents. These events seem to be independent of the cumulated dose. These findings draw attention to the cardiovascular side effects of interferon-alpha and advise prudence in high-risk patients.