This study suggests that paternal occupational lead exposure may be associated with low birth weight in the offspring. The odds of low birth weight rose fivefold among infants of fathers who were potentially exposed to high levels of lead during the period 6 months before pregnancy to the end of pregnancy (adjusted odds ratio (aOR) = 4.7, 95% confidence interval (CI) = 1.1-20). This effect was most prominent for low-birth-weight infants who were both preterm and small for gestational age. There was a suggestion of a gradual increase of the odds of low birth weight at medium levels of exposure, but this increase was not statistically significant. No increased odds was observed at low levels of exposure. Low birth weight was not associated with paternal ever versus never exposure, indirect exposure, or exposure frequency. An independent effect of exposure duration could not be evaluated as it was highly correlated with exposure level.