The association between ventricular premature complexes (VPCs) detected on a rest 2-minute lead I electrocardiographic rhythm strip and sudden cardiac death (SCD), occurring within 1 hour of onset of symptoms, was evaluated in a prospective study of 15,637 apparently healthy white men, aged 35 to 57 years, at the first screening examination (1973 to 1975) to determine eligibility for the Multiple Risk Factor Intervention Trial in Minneapolis/St. Paul, Minnesota. The prevalence of any VPC was 4.4% (681 of 15,637). Over an average follow-up period of 7.5 years, a total of 381 deaths occurred. Of these, 34% (131 of 381) were ascribed to coronary artery disease (CAD) and 31% of the CAD deaths (41 of 131) occurred suddenly. The presence of any VPC was associated with a significantly higher risk for SCD (adjusted relative risk = 3.0; p less than 0.025). On the other hand, the presence of any VPC was not associated with any significant increase in the risk of non-SCD or of total deaths from CAD (adjusted relative risk = 1.0 and 1.6, respectively). When VPC characteristics such as frequency (2 or more uniform VPCs every 2 minutes) and complexity (multiforms, pairs, runs, R-on-T) were examined, those with frequent or complex VPCs were at a significantly increased risk of SCD (adjusted relative risk = 4.2; p less than 0.005), whereas for non-SCD no significant increase in risk was found (adjusted relative risk = 1.6; p = 0.28).(ABSTRACT TRUNCATED AT 250 WORDS)