Two hundred four neonates, 25 to 42 weeks estimated gestational age (EGA), were measured on day 2 or 3 of life for upper mid-arm circumference (MAC) and head circumference. Regression analysis was used to construct standard curves for MAC versus EGA and mid-arm circumference/head circumference ratio (MAC/HC) versus EGA. Correlation coefficients were 0.93 for MAC versus EGA, and 0.84 for MAC/HC versus EGA. MAC, MAC/HC, and head circumference were also highly correlated with birth weight. These measurements may more accurately assess intrauterine growth and body proportionality at birth than weight, length, and head circumference.