This study involves treating individuals with the Smith-Lemli-Opitz syndrome, a rare inborn error of cholesterol metabolism, with supplemental cholesterol to determine it effects on biochemical sterol metabolites, growth, neuropsychological development, ophthalmologic and auditory function, ERG (electroretinogram) parameters, and CNS metabolites as determined by brain MRS-imaging. Safety of the supplemental cholesterol suspension is monitored by tests of hematologic, renal, and liver function at periodic intervals. There is also a substudy that is investigating potential genotype-phenotype correlations, as well as another that studies biochemical parameters of light sensitivity in cultured skin fibroblasts from affected patients.