This paper is an attempt to investigate the differentials and determinants of age at menarche according tothe characteristics of females. Simple average, univariate as well as multivariate analysis were carried out.A multivariate technique has been utilized to study the effect of various socio-economic variables on thetiming of menarche.The data for this study were taken from a sample survey of Palpa and Rupandehi Districts” conductedbetween January and June 2000. A total of 1258 (including 239 daughters and 1019 mothers) femalesprovided information on the age at menarche. For this study only 239 samples of young girls have beenanalysed.Mean age at menarche was found about 15 and 14 years for older generation (mothers) and youngergeneration (their daughters) respectively. A decreased age at menarche was found with the increased levelof socio-economic status group of girls. Age at menarche was found higher for girls belonging to nonschooling(15.7 years) as compared to the schooling girls (14.2 years). It was found that the variables ‘socioeconomicstatus’, and ‘caste/ethnicity’ were the significant determinants for the timing of menarche. Ahigher risk of getting menarche early was found for high socio-economic status and schooling girls ascompared to the low socio-economic and non-schooling, which may be due to nutrition and physical andpsychological stress during the early childhood.Key Words: Fertility, Menarche, Differentials, Determinants, Reproductive, Adolescent, Sub-fecundity, Foetal wastage.