Genomic DNA was isolated from two related individuals who are homozygous for transcortin Leuven, a corticosteroid-binding globulin variant with decreased cortisol-binding affinity. This material was amplified using intron-specific oligonucleotide primers in a polymerase chain reaction to obtain the four exons that encode transcortin. Sequence analysis of these exons showed several mutations within the coding sequence of both individuals, but only one of these will result in an amino acid substitution. This mutation is located within exon 2 and alters the codon (CTC) normally associated with Leu-93 in the transcortin polypeptide to a codon (CAC) for histidine in the variant genes.