Linkage studies between X-linked adrenoleukodystrophy and a cloned deoxyribonucleic acid fragment (St14), which detects polymorphisms in the distal end of the long arm of the X chromosome (Xq27-28), have shown no recombination in six families. The lod score for these data (and another kindred reported earlier is 13.766 at recombination fraction (theta) = 0.0. These data permit assignment of adrenoleukodystrophy carrier status in family members at risk, supplementing the chemical measurement of very-long-chain fatty acids.