The study compares biological, socioeconomic and behavioural determinants of low birthweight in Cameroon and the United States. Some factors in low birthweight are found to be cross-national, but others are specific to the setting. Positive risk factors of low birthweight in both countries include unmarried motherhood, female sex, multiple births, and preterm births. Outcome of the previous pregnancy is a positive risk factor in the US, but not in Cameroon. Significant negative risk factors include prenatal care visits (in both countries), mother's education (in the US only), births to mothers aged 20-34 and birth orders of 2 or more (in Cameroon only). Separate analyses of all births and the subsamples of singleton births reveal that estimates for the two groups differ only marginally.