Previous reports from our group have shown that birth weight is associated with mortality rate during the neonatal and postnatal periods and that low arm circumference at birth (LACB: equal or less than 9.0 cm), is closely correlated with birth weight. This paper explores the relationship between arm circumference at birth and early mortality. For this purpose, 823 newborns were studied. Of these, 416 had a normal ACB (larger than 9.0 cm) and 407 were LACB (high risk group). In addition to arm circumference, weight, height, chest and head circumferences were measured during the first 24 hours after birth. Both groups were followed-up during 14 days. All the 27 deaths observed in the study infants occurred in the LACB group (p<0.001). Relative risk of death during this period was 10 to 17 times higher in the LACB group than in the low risk group (p<0.001). Estimated sensitivity and specificity of LACB were 100 per cent and 84 per cent respectively. These results indicate that, as suggested before, arm circumference at birth equal or less than 9.0 cm is a useful indicator to predict risk of death during the first fourteen days of life in areas where birth weight assessment is not feasible. © 1983 Oxford University Press.