Interleukin-1 (IL-1) plays a key role in inflammation, has an effect on a wide variety of cells, and often leads to tissue destruction. While the ratio between IL-1 and IL-1Ra could influence the development of different diseases of the central nervous system, its gene polymorphisms were investigated in a group of patients with febrile seizures. Ninety patients with febrile seizures were enrolled and compared with 140 controls. The allele and genotype frequency of single nucleotide polymorphisms within the IL-1α, β, IL-1 R and IL-1Ra gene were determined. The frequency of the IL-1Ra/C allele at position Mspa-I 11100 was decreased significantly (P=.002) and the IL-1Ra/T frequency was significantly increased in patients (P=.002). In addition, the CT genotype frequency at the same position was significantly overrepresented in controls compared to patients (P=.001). Certain alleles and genotypes in the IL-1 gene were overrepresented in patients with febrile seizures, which possibly could predispose individuals to this disease.