We aimed to assess prevalence and correlates of hazardous use of tobacco, alcohol and other drugs in a primary care population in Cape Town, South Africa. Stratified random sampling was used to select 14 of the 49 clinics in the public health sector in Cape Town, and every "nth" patient, with those ages 18-25 oversampled (N = 2,618). Data were collected from December 2003 through 2004, using the World Health Organization Alcohol, Smoking, and Substance Involvement Screening Test. Hazardous use of tobacco was most common, followed by alcohol and then other drugs. Hazardous tobacco use was associated with the 18-25 years age group, no religious involvement, high school completion, and higher stress. Hazardous alcohol use was associated with male gender, younger men, no religious involvement, employment, some high school education, and higher stress. Hazardous use of other drugs was associated with Colored (mixed) race (particularly among men), no religious involvement, employment, and stress. For all substances, women, particularly Black women, had the lowest rates of hazardous use. Although the study is cross-sectional, it does identify groups that may be at high risk of substance misuse and for whom intervention is urgent. Because prevalence of substance use is high in this population, routine screening should be introduced in primary care clinics. (Parry, 2005;Sitas et al., 2004). Cannabis and methaqualone are the most frequently identified illicit drugs in drugrelated arrests, psychiatric diagnoses, and trauma patients (Parry et al., 2002), but treatment demand for cocaine, heroin, and methamphetamine use is increasing Parry, Myers, and Plüddemann, 2004).Primary health care services provide an advantageous location for intervening in substance use (Whitlock, Polen, Green, Orleans, and Klein, 2004;Fleming et al., 2002). In South Africa, the public health sector is the main provider of primary care (Health Systems Trust, 2004), yet no data are available on prevalence of substance misuse among South African patients.Risk factors are those associated with increased likelihood of negative health behaviors or outcomes, whereas protective factors are those that are associated with increased likelihood of positive health behaviors or outcomes, or with decreased likelihood of negative health behaviors or outcomes (Kirby, 2001). Although the association with disease occurrence may not be causal, such correlates are useful for identifying high-risk groups or factors that may be usefully targeted in intervention strategies. Risk and protective factors influencing substance use have not been much studied in the developing world (De Lima, Dunn, Novo, Tomasi, and Reisser, 2003).Personal characteristics identified as risk factors may include age, race, and gender. In South Africa, the racial categories defined under apartheid-Black, Colored (mixed race), Indian, and White-have a long association in South Africa with access both to alcohol and to treatment (Mager, 2004). Different race groups may demonstrate differen...