To examine the effects of maternal prenatal smokeless tobacco use on infant birth size. Design. A retrospective medical record review of 502 randomly selected deliveries. Population and Setting. Singleton deliveries to Alaska Native women residing in a defined geographical region in western Alaska, 1997–2005. Methods. A regional medical center's electronic records were used to identify singleton deliveries. Data on maternal tobacco exposure and pregnancy outcomes were abstracted from medical records. Logistic models were used to estimate adjusted mean birthweight, length and head circumference for deliveries to women who used no tobacco (n=121), used smokeless tobacco (n=237) or smoked cigarettes (n=59). Differences in mean birthweight, length and head circumference, 95% confidence intervals and p-values were calculated using non-users as the reference group. Main Outcome Measures. Infant birthweight, crown–heel length and head circumference. Results. After adjustment for gestational age and other potential confounders, the mean birthweight of infants of smokeless tobacco users was reduced by 78g compared with that of infants of non-users (p=0.18) and by 331g in infants of smokers (p<0.01). No association was found between maternal smokeless tobacco use and infant length or infant head circumference. Conclusions. We found a modest but non-significant reduction in the birthweight of infants of smokeless tobacco users compared with infants of tobacco non-users. Because smokeless tobacco contains many toxic compounds that could affect other pregnancy outcomes, results of this study should not be construed to mean that smokeless tobacco use is safe during pregnancy.