This paper explores several extensions to the variance component method, which incorporate genotype x age interaction effects. We evaluate the performance of these methods for detecting genotype x age interaction in quantitative genetic analyses of a quantitative trait (Q4), contrasting this with false positive detection rates obtained from a phenotype influenced by the same genes but without genotype x age interaction effects (Q3). We then assess the impact on linkage power and false positive rate of allowing a QTL-specific genotype x age interaction in linkage analysis of these same traits.