A parametric algorithm was developed for computing model cohort and period survival functions used in making projections of human populations. Two levels of parameters were used in developing the algorithm. The algorithm provides a method for calculating model period survival functions as a function of an expectation of life at birth; model cohort survival functions are calculated as a function of a time series of period expectations of life at birth. Expectations of life at birth ranging from about 35 to 110 years in both sexes may be accommodated by the algorithm.