The influence of shared environmental factors on adolescent adjustment was investigated in a sample of 667 adoptive families. Correlations between parental ratings of family functioning and adolescent ratings of adjustment were generally higher for birth offspring than for adoptive offspring, suggesting passive genotype-environment processes. For all except one of the indicators of adolescent adjustment, the nonbiological sibling correlation was low, suggesting that approximately 10% or less of the variance in these measures is attributable to shared environmental effects. However, for a quantitative measure of alcohol and tobacco use, the nonbiologically related sibling correlation was moderate (r = .26) but most consistent with sibling rather than parent effects. These findings provide further evidence of the minimal effect of common rearing on sibling psychological similarity, at least within the broadly constituted U.S. middle class.