The estimation of various forms of genotype-environment (GE) correlation is considered. Two methods of estimating “passive” GE correlation from adoption studies are presented and illustrated with IQ data from five adoption studies. One method involves comparison of variances in adoptive and nonadoptive families, whereas the other compares parent-child correlations in such families. The second method yields more precise results for given sample sizes. Ignoring measurement errors leads to marked underestimation of GE correlations. Application of these methods to available adoption data on IQ suggests that typical passive GE correlations for IQ lie in the neighborhood of 0.30.