SummaryInfant mortality in Sri Lanka between 1961 and 1980 is studied with reference to its trend and associated factors. Between the periods 1961–65 and 1976–80 deaths from exogenous and endogenous causes have declined considerably and nearly equally. The probability of survival has increased most in the first week of life.National income or total food supply does not seem to be associated with infant mortality. Distribution of free supplementary food, increase of public health personnel, of immunization, and of institutional births appear to have initiated and sustained the transition of infant mortality during the period. Increasing levels of female education probably augmented these effects.