Risk factors for late fetal death and early neonatal mortality were examined in a population based prospective study. Practically all Swedish births between 1983 and 1985 were included, 281,808 births in all. The overall rates of late fetal death and early neonatal mortality were 3.5 and 3.1 per 1000, respectively. About 30% of the pregnant women were recorded as being daily smokers. Logistic regression analyses showed significant relative risks for late fetal death for high maternal age (1.4), nulliparity (1.4), multiparity (greater than or equal to 2) (1.3), smoking (1.4), and multiple births (2.8). Significant relative risks for early neonatal mortality were found for multiple births (4.9) and smoking (1.2). Smokers aged under 35 faced a relative risk of late fetal death ranging from 1.1 to 1.6, while the risk for late fetal death was doubled if the mothers were aged 35 years or more and smoked. In countries like Sweden, where maternal cigarette smoking is prevalent, smoking may be the most important preventable risk factor for late fetal death.