Sclerosteosis is a rare, potentially lethal skeletal disorder in which massive bony overgrowth leads to facial distortion, cranial nerve compression and progressive rise in intra‐cranial pressure. Gigantism and syndactyly of the 2nd and 3rd fingers are associated features. In a nationwide investigation in South Africa, 25 affected individuals in 15 Afrikaner kindreds have been studied. The minimum prevalence of the condition in this community is 1 in 75,000. Analysis of pedigree data confirms that sclerosteosis is an autosomal recessive condition. The gene frequency in the Afrikaner people is estimated at 0.0035, with 10,000 clinically normal heterozygotes in this population. Heterozygote detection may be possible on a basis of recognition of minor changes which are apparent on skull radiograph