Interleukin (IL)-1 is markedly overexpressed in the brains of patients with Alzheimer's disease (AD). We aimed to evaluate the relationship between three polymorphisms of the IL1 gene (IL-1beta promoter -511T/C, IL-1beta exon 5 E1/E2 and IL-1-RA) and late onset AD in Taiwan Chinese. Forty-six late onset AD patients and 103 unrelated, age-matched, healthy controls living in the same area were included. PCR was used to resolve the two IL-1beta polymorphisms and the IL-1Ra intron 2 polymorphism. The -511T/T type of the IL-1beta promoter (unlike IL-1beta exon 5 and IL-1-RA) was more frequently found in AD than in healthy patients (-511C/C type versus T/T type, OR = 0.944, CI = 0.393, 2.269, P = 0.898; -511C/T type versus T/T type, OR = 0.375, CI = 0.156, 0.902, P = 0.028). The -511T/T genotype (unlike the other two polymorphisms) is a marker demonstrating that late onset AD in Chinese patients in Taiwan is genetically determined.