Several studies investigating the role of the CCR5delta32 mutation in multiple sclerosis (MS) have reported varied, often contradictory results. Therefore in the present study we have analysed whether the CCR5delta32 mutation is associated with the risk of/or disease process in Croatian and Slovene MS patients. Three hundred and twenty-five MS patients and 356 healthy controls were genotyped by the polymerase chain reaction method. Our results showed no significant differences in the distribution of CCR5delta32 mutations between MS and control subjects, indicating that this mutation does not influence susceptibility to MS. Furthermore, we did not observe that CCR5delta32 carrier-status could modulate age of disease onset or progression of the disease. It is therefore our conclusion that the present study indicates that the CCR5delta32 mutation is neither protective of, nor a risk factor, for MS development.