The objective of this study was to examine the possible relationships between spontaneous abortion and caffeine, tobacco and alcohol intake in a well-controlled group of hospital workers. A retrospective cohort study design including 711 women, 20 to 41 years old, was used. All data regarding the purpose of this study were extracted from clinical histories registered at the Preventive Medicine Service. The dependent variable was spontaneous abortion and the independent variables were tobacco, coffee, and alcohol intake. Age, previous spontaneous abortion, menarcheal age and marital status were considered as potential confounders. The data were analyzed by multiple logistic regression. The following adjusted odds ratios of spontaneous abortion by caffeine consumption were calculated: 141-280 mg/day, 2.20 (1.22-3.96); 281-420 mg/day, 4.81 (2.28-10.14) and 421 or more, 15.43 (7.38-32.43); p < 0.05. The adjusted odds ratio for tobacco were 11 or more cigarettes/day, 3.35 (1.65-6.92); p < 0.05. It appears from this and other papers that tobacco and caffeine intake must be considered as clear risk factors for spontaneous abortion or miscarriage.