Objective: To assess birthweight, length and head circumference of live births, and to examine the effect of maternal age, parity and gestational age on birth sizes of the live births.Design: A prospective study.Setting: Tikur Anbessa, Zewditu, Gandhi memorial and St. Pauls hospitals, in Addis Ababa, Ethiopia.Subjects: Four thousand two hundred and six consecutive live births from July 1996 to January 1997.Main outcome measures: Weight, length and head circumference of the newborns.Results: Among the 4206 consecutive live births, 4047 were singleton and 159 were twins. Two thousand one hundred and sixty (51.7%) were males and 2046 (48.6%) were females. The mean birthweight of singleton live births was 3065 465 g, with modal group of 3000-4000 g. The incidence of low birthweight was 9.1%. The mean length for all singleton live births was 48.6 ± 3.3 cm and modal group of 46-52 cm. The mean head circumference was 34.4±2.9 cm; modal group 31-37 cm. The incidence of low birthweight of the newborns was significantly higher for females, younger maternal age, primiparas and pre-term babies. On the multivariate analysis, gestational age and sex of the newborn respectively had significant effects on birthweight, length and head circumference of the neonates controlling for the other variables. on the other hand parity and maternal age had significant effects only on the birthweight of the neonates.Conclusion: This study has provided information on the effects of some of maternal characteristics on the size, particularly length and head circumference of newborns which were not given emphasis on previous birthweight studies. We suggest proper recording and analysis of birthweight, length and head circumferences be given importance for monitoring and evaluating maternal and child health programmes.