The affinity and turnover of the specific dihydrotestosterone binding protein have been assessed in fibroblasts cultured from genital skin from a variety of control subjects and from 4 patients with incomplete hereditary male pseudohermaphroditism due to androgen resistance (incomplete testicular feminization and Reifenstein syndrome). Whereas the amount of dihydrotestosterone binding in the 4 mutant cell strains is low, both the affinity of the protein for dihydrotestosterone as assessed by the concentration at which half-maximal binding occurs (averaging 0.2 nM) and the turnover of the binding protein (average half-life of 11--13 h) are within the normal range. Since no qualitative abnormality could be detected, these data suggest that the mutations in these two disorders affect the synthesis of the dihydrotestosterone binding protein.