Power to detect linkage and localization of a major gene were compared in univariate and bivariate variance components linkage analysis of three related quantitative traits in general pedigrees. Although both methods demonstrated adequate power to detect loci of moderate effect, bivariate analysis improved both power and localization for correlated quantitative traits mapping to the same chromosomal region, regardless of whether co‐localization was the result of pleiotropy. Additionally, a test of pleiotropy versus co‐incident linkage was shown to have adequate power and a low error rate. © 1997 Wiley‐Liss, Inc.