Variance component methods are now being used in linkage analysis to detect genes influencing complex diseases. These methods are easily extended to allow for simultaneous estimation of both the additive effects of multiple loci on phenotypic variation (conditional oligogenic analysis) and the additive interaction (epistatic) effects among loci. We performed linkage analyses on 200 of the simulated replicates in order to evaluate the power to detect the main effects of MG1and MG2 on Q1 as well as their interaction effects. The power to detect the main effect of MG1 was moderately good, although the power to detect MG2 and the MG1×MG2 interaction was poor. © 1997 Wiley‐Liss, Inc.