According to several studies breast cancer is more common among former smokers. This study explores whether this association has any relationship with anthropometric measurements or blood lipid levels. The 2082 ex-smokers (mean age 49.9 years) in the Malmö Preventive Cohort were followed for an average of 13.3 years using official cancer registries. This yielded 93 incident breast cancer cases. Oestrogen receptor (ER) status was assessed by an immunological method. Incidence of breast cancer covaried with height, body mass index, weight gain and cholesterol levels. None of these associations reached statistical significance. Incidence of breast cancer increased over quartiles of serum triglycerides, Ptrend: 0.02, relative risk (RR) for triglycerides as a continuous variable: 1.46 (1.21-1.77). Nineteen tumours were ER negative; this subgroup was similarly related to high triglycerides, 1.76 (1.40-2.21). All results were similar when BMI and cholesterol levels were entered into the model. It is concluded that breast cancer incidence covaries with triglyceride levels in ex-smokers.