The size and the time of closure of anterior fontanel (AF) is often used in the diagnosis ofrndisorders like altered skeletal morphogenesis, increased intracranial pressure, hormonalrndisorders and others. In order to properly utilize AF size in the diagnosis of differentrndisorders, it is necessary to establish a normal range of AF sizes related to age. Racialrndifferences in the size of AF and its time of closure has been reported and there are manyrncountries with their own national standard. To my knowledge, there is no study done torndetermine the AF size and its time of closure in Ethiopian neonates and infants.rnThe present study aims to establish mean AF size for Addis Ababa (A.A.) neonates andrninfants at the ages of 3, 46, 76, 106 and 270 days.rnThe study is a cross sectional design carried out from January 2003 to December 2003 inrnA.A. and the study sites chosen were Tikur Anebessa Specialized Hospital, ZewditurnMemorial Hospital, Tekele Haymanot and Wereda 23 Health Centers. The subjects werern687 neonates and infants, of which 363 were males and 324 were females. All casesrnfulfilling the inclusion criteria were included in a row until the targeted sample size wasrnattained. The AF size, body weight, body length and head circumference were measured.rnWhen measuring AF size, first the four vertices were identified. After marking thernvertices with washable ink, the marks were transferred on a sheet of paper. From thernmarks transferred on the sheet of paper, the anterior-posterior and the lateral dimensionsrnwere measured. The mean of the anterior-posterior and the lateral dimensions was takenrnas AF size.rnThe mean AF size progressively decreased with age except at 106 days measurementrnwhich showed increase over the 76 days measurement. In all ages considered, nornsignificant difference (p>0.05) was found in neonates and infants of different gender,rnbirth order, gestational age and economic status. AF closure was observed beginning atrnthe age of 76 days (0.8%) and the percent of closure increased with age. In Infants at thernage of 270 days, 39.6% of them had closed AF. There were no significant (p>0.05)rncorrelations between AF size and body weight, body length and head circumferencernwhile there was negative significant (p