Adequate child spacing is considered as a posilive factor on Ihe health of mothers and theirrnchildren. The birth interval has been reported to have significant effect on the child'sfoturernphysical and mental capabilities. However, lillie or no allempt has been made to identify thernsocio economic, demographic and biological determinants of birlh interval length usingrnprimary data in the study area. The general objective of this study was an investigation of thernkey factors affecting birth interval length in Fagita Lekoma woreda. For this purpose, crossrnsectional study was conducted in three kebeles of Fagita Lekoma Woreda, Awi AdministrativernZone. For this study, 504 eligible women (women who had at least two children) werernselected by using systematic random sampling technique.rnIn order to investigate the effects of co variates on the dependent variable, Cox proportionalrnhazard model was used. In bivariate analysis, the Kaplan Meier median length was used tornexamine birth interval differentials by socio economic, demographic and biologicalrncharacteristics of women. The results indicated that almost in all birth intervals, educatedrnwomen, working women, Protestants, urban women, women belonging to the Agew ethnicrngroup, women whose index child has survived, women who had married at 18years of age orrnajier and women who used family planning programs have longer birth interval lengths.rnIn multivariale analysis, work status, contraceptive use and survival status of the index childrnwere consistently significanl while age at first marriage and place of residence werernsignificant in some birlh inlervals.rnIt is recommended that concerled efforl be made to enhance female educalion, their laborrnforce participation, expand coverage of family planning services and increase age at firstrnmarriage