Summary. A population-based retrospective case-control study has been conducted in Tasmania since October 1988. Study measurements pertained to the scene of death of last sleep, as well as a verbal questionnaire on relevant exposures. From 1 October 1988 to 1 October 1991, 62 cases of sudden infant death syndrome (SIDS) occurred. Case response rate for retrospective interviews was 94% (58/62). The initial control response rate was 84% (101/121). After stratification for maternal age and birthweight, there was no increase in risk associated with the usual side position (odds ratio [OR] 1.05 [0.27, 5.02]), compared with the supine position (OR 1.00, reference). The prone position was associated with increased risk [OR 5.70 (1.67,25.58)], relative to the supine position. In the final multivariable model, predictors of SIDS in this study were usual prone position (P < 0.001), maternal smoking (P = 0.008), a family history of asthma (P = 0.045) and bedroom heating during last sleep (P = 0.039). Protective factors were maternal age over 25 years (P = 0.013) and more than one child health clinic attendance (P = 0.003). The results provide further support for current health education activities which aim to inform parents of modifiable risk factors for SIDS, including the prone sleeping position, thermal stress and infant exposure to tobacco smoke.