SummaryThe limits to artificial selection for pairs of linked additive loci of equal proportionate effect, starting from a base population in linkage equilibrium, have been studied by means of a simulation technique on a CDC 3600 computer. Particular attention has been paid to the case of genes of large effect, making use of the definition of the selective value of a genotype given in the first paper of this series.It has been shown that the expected total response is progressively reduced as the degree of linkage is intensified, the effect being most pronounced when the response due to unlinked genes is expected to be 60-70% of the maximum possible advance. The magnitude of the reduction observed in these experiments is appreciable only at recombination values less than 0 ·10. It is concluded that if the effects of population size alone are such as to reduce the expected response by 40% or more, the linkage effect may be relatively unimportant for genes separated by as little as five map units.