The third birth transition has a negative impact on the national goal of fertility replacement level (2.1) which is to be achieved by 2010. To identify the factors influencing the demographic phenomenon, a cross sectional as well as community based study consisting of 1397 eligible women was conducted in the four valley districts of Manipur under cluster sampling scheme. Analysing the empirical information through SPSS, 42% of the study subjects transit their 3rd birth and its major determinants could be detected to be sex preference, age at marriage, and educational level each at 0.01 probability level of significance