The one-year prevalence and correlates of selected DSM-III-R disorders were determined in a sample of 930 18-year-olds. Using both diagnostic and impairment criteria 340 individuals (36.6%) were considered to have disorder. The most prevalent disorders were major depressive episode (16.7%), alcohol dependence (10.4%) and social phobia (11.1%). There was a high degree of co-morbidity among disorders; 46% of those with disorder had two or more. The prevalence of disorders was greater for females, with the exception of conduct disorder and alcohol or marijuana dependence. A variety of characteristics were associated with disorder, including poor social competence, disadvantage and self-rated health status. A third of those with disorder had their problems recognised by a "significant-other". The results are presented within the context of a perceived need for research in the area of adolescent and early adult mental health in order to minimise the toll of mental disorder in later life.