Several studies have examined whether a dimorphism in the CD152 costimulatory molecule may influence the development of multiple sclerosis (MS). A sample of 108 patients with a diagnosis of relapsing remitting (RRMS), 28 with secondary progressive (SPMS), 23 with primary progressive (PPMS) and 63 people with no prior history of neurological conditions were selected from the MS clinic at the University of Texas Southwestern Medical Center at Dallas. Peripheral blood was separated with gradient extraction for leukocytes and genomic DNA extracted for CD152 A/G dimorphism analysis. A 163 bp PCR product in exon 1 including the position 49 A/G dimorphism was examined via single strand conformation polymophism (SSCP). Patient haplotype frequencies were compared between cases and controls and Pearson Chi-Square test performed to demonstrate statistical differences between MS groups and controls. Our results, similar to several recent studies, suggest that there is no statistical association with the risk of developing MS and no increased frequency in A or G at position 49 of exon 1 of CD152. Demonstration of prolonged proliferation in patient samples containing the GG genotypes and altered CD152 surface expression was also not demonstrated suggesting that the CD152 exon 1 position 49 A/G dimorphism does not contribute significantly to the development of MS in this patient population.