The Elston–Stewart algorithm is a recursive algorithm that allows one to calculate the pedigree likelihood of an oligogenic model as a function of founder genotypic probabilities, penetrance functions, and genetic transition probabilities. The amount of time required for the computation increases linearly with the size of the pedigree, but exponentially with the number of loci in the genotype. In contrast, the Lander & Green algorithm has computational time that increases exponentially with the size of the pedigree, but linearly with the number of loci. An analogous algorithm allows the likelihood to be calculated for a pedigree of n individuals under polygenic inheritance without needing the inversion of an n × n symmetric matrix.