Mutations in CYP21 (21-hydroxylase) leadto congenital adrenal hyperplasia (CAH). Wegenotyped 26 probands with CAH by PCRsequencingthe entire CYP21 gene. 25/26 hadhomozygous or compound heterozygous mutations.The frequencies of mutations were similarto other populations with deletion/hybrid, 12 Gsplice and I172N the most common. Fivepatients with a 1172N allele predicting simplevirilisingCAH had a salt-wasting phenotype.Two other probands also had a more severephenotype than predicted by genotype. Twofamilies had both non-classic and salt-wastingphenofypes arising from combinations of threedeleterious alleles. Two novel CYP21 alleles weredetected: D106N and a large deletion encompassingCYP21 and adjacent pseudogene. Tworare CYP21 alleles were also found. Three ofthese four novel/rare alleles were only detectedas a result of sequencing the entire CYP21 gene.Entire CYP21 sequencing will increase thenumber of mutations detected in CAH, and incombination with functional studies shouldcontribute a greater understanding of phenotype-gcnotype correlations.