Temporal changes in Reproductive fitness – A case study of Fertility and Mortality in Dhaneshwar Saundik, the predominant Vaishya population of Munger district, Bihar has been studied in respect of their reproductive adaptability and frequency distribution of certain somatotopic and genetic characters. Reproductive adaptability has been studied on the basis of the parameters of marriage practices like the incidence of marriage, the age of mother at the time of marriage. The certain natural phenomenon like age at menarche (13.49years), age at menopause (49.51 years), sterility (ever and never pregnant), fertility and mortality have been studied. The mean number of children per mother has also been calculated and it has decreased by 2.18 %. In our studies the Infant mortality rate (IMR), adolescent mortality rate (AMR) and net reproductive index (NRI) also shows a declining trend.