The spectrum of mutated alleles in non-classical congenital adrenal hyperplasia (NC-CAH) has been recently reported to be very large and haplotypes may significantly differ in the different ethnic groups. In order to confirm that population differences may exist in the genetic basis of this disease, we have analyzed the genetic presentation of NC-CAH in a Sicilian cohort of symptomatic patients and compared our findings with the ones reported in other studies of different ethnic groups. In 38 NC-CAH patients coming from two regions of Sicily and born of Sicilian parents, we found that 84.2% of the chromosomes examined bore only mild mutations and only the remaining 15.8% of the chromosomes bore at least 1 severe mutation. The overall predominant mutation was V281L, which was detected in 73.7% of alleles and in 89.5% of patients. About 58% of the patients were homozygotes for this mutation. V281L allele and homozygote frequencies were higher in the present series than in other European and Italian reports. In our NC-CAH population, which is one of the largest ever reported, the patients with two mild mutations exhibited a less severe impairment of both clinical and endocrine phenotype. On the basis of these results we can conclude that: a) in Sicilian ethnic groups NC-CAH is frequently associated with a very mild genotype; b) the most frequent genotype in our series is V281L homozygosis; c) clinical and biochemical expression of NC-CAH is more marked in the patients bearing a severe mutation; d) no correlations between genotype and phenotype were found in our patients affected by NC-CAH.