Children with conduct disorder have long been known to be at high risk for developing externalizing disorders, alcohol and drug abuse, and antisocial personality. Relationships of conduct disorder to other adult psychiatric disorders, on the other hand, have not been definitively shown. Taking advantage of the large community sample (N = 19,482) interviewed in the NIMH Epidemiologic Catchment Area Program, the authors examined the effects of childhood conduct problems on ten DSM-III psychiatric disorders: somatization, phobia, panic, obsessive-compulsive, depression, mania, alcohol use disorder, drug use disorder, schizophrenia and antisocial personality. Each of the ten adult disorders showed an increase in prevalence with an increasing number of conduct problems, although effects were stronger for externalizing disorders. The predictive power of conduct problems was similar for males and females. The effect of conduct problems on nonexternalizing disorders was found to be largely mediated through externalizing disorders, particularly for men but direct effects also occurred for both sexes. These findings raise questions about the conventional view of psychiatric disorders as divisible into externalizing and internalizing disorders. They also suggest that the increasing rates of conduct problems in younger cohorts may be responsible in part for the rising rates of other disorders. Thus, prevention of and early intervention with conduct disorder may hold promise for reducing rates of a broad range of disorders.