This study was performed to investigate the association between interferon (IFN)-gamma single nucleotide polymorphism (SNP) and susceptibility for psoriasis vulgaris. DNA from 78 patients with psoriasis vulgaris (54 patients with type I psoriasis, 24 with type II psoriasis) and 74 healthy volunteers was investigated. IFN-gamma promoter gene SNP in position 874 was evaluated by polymerase chain reaction with sequence-specific primers (PCR-SSP) and the results were compared between a group of psoriatic patients, divided into early onset of psoriasis (type I) and late onset of psoriasis (type II) subgroups, and healthy control subjects. A significant difference in the genotype frequencies between psoriasis patients and healthy controls was found (p < 0.02) and no significant differences were observed analyzing subsets of psoriatic patients (gender, type of disease) also in carriage and allele frequencies. The results suggest that IFN-gamma polymorphism is associated with susceptibility to psoriasis vulgaris.