There have been a number of national surveys of psychiatric morbidity, which have included questions on drugs, alcohol, and tobacco. These surveys have helped delineate the overlap between substance use and dependence and other psychological morbidity. There is a strong association reported between high substance consumption and other measures of psychological problems. This article provides an overview of a national household survey, a survey of institutional residents with psychiatric disorders, and a national survey of a homeless population. fill three surveys used comprehensive and complex sampling strategies and lay interviewers to conduct structured diagnostic interviews. The household survey included over 10,000 households, the institutional survey interviewed 755 individuals, and the homeless survey of hostels, night shelters, day centres, and private sector leased accommodation interviewed 1,061 individuals. This overview looks at patterns of nicotine, alcohol, and other drug use in the different samples and examines interactions with other psychiatric morbidity. The survey reports that substance-related disorders are some of the commonest disorders in the community, with 5% of the household sample alcohol dependent 7% alcohol dependent in the institutional sample and over 21 % in the homeless sample recorded as alcohol dependent. Tobacco, alcohol and other drug use and dependence were dramatically higher in the homeless sample than in either of the other two samples. Substance use was significantly associated with higher rates of psychological morbidity as measured by the Clinical Interview Schedule Revised. Future service planning needs to take account of the striking disparity of prevalence of psychiatric disorders in different subsections of the population. (Author's abstract.)