The potential effects of paternal exposures on fetal development are of great public and scientific concern, yet few epidemiologic studies have examined this association. Single live births from 1959 to 1966 among 14,685 Kaiser Foundation Health Plan members who participated in the Child Health and Development Studies were analyzed to assess the impact of paternal age, cigarette smoking, and alcohol consumption on the occurrence of birth defects in the offspring. Prevalence odds ratios for anomalies identified by age 5 were analyzed, contrasting exposed to unexposed fathers with adjustment for maternal age, race, education, smoking, and alcohol use. Advanced paternal age was associated with increased risk of preauricular cyst, nasal aplasia, cleft palate, hydrocephalus, pulmonic stenosis, urethral stenosis, and hemangioma. Father's cigarette smoking was more common among children with cleft lip ± cleft palate, hydrocephalus, ventricular septal defect, and urethral stenosis. Alcohol use by the father was most positively related to the offspring's risk of ventricular septal defect. For both smoking and alcohol use, inverse associations were more common than positive associations. These data generally do not indicate strong or widespread associations between paternal attributes and birth defects. However, because of this study's imprecision, limited ability to isolate defects most likely to be of paternal origin, and the identification of several suggestive associations with age and smoking, further study of this issue would be of value.