Covariance models of selection predict gene frequency change in terms of the relationship between the fitness of an individual and its phenotype, and therefore provide a convenient method for studying evolution in natural systems. When these models are partitioned into effects acting within and between hierarchical levels of selection, they can be directly applied to questions of kin selection. In many cases, the partitioning of covariance approach to the study of kin selection is a more useful alternative to the traditional hamiltonian or inclusive fitness approach. © 1990.