A study was conducted to determine whether expectant mothers' cigarette smoking reduces the bone mineral content of their new born babies. A sample of 80 newborns whose mothers smoked during pregnancy has mean bone mineral content of 0.075 g/cm and standard deviation of 0.020 gm/cm. A sample of 160 newborns whose mothers did not smoke during pregnancy has mean bone mineral content of 0.090 g/cm and standard deviation of 0.023 gm/cm. Using 5% significance level test whether expectant mothers' cigarette smoking reduces the bone mineral content of their new born babies.