Objective: A genetic polymorphism in the interleukin 1 gene has been implicated as a factor in determining the severity of adult periodontitis. Among white Europeans, the prevalence of genotype-positive subjects has been reported to be around 30%. The purpose of this study was to assess the prevalence of genotype-positive individuals in a Hispanic population. Method and materials: Fifty Mexicans were evaluated for their interleukin 1 genotype with a commercially available test. Subjects were divided into groups, as determined by their genotype (positive or negative), and were then analyzed according to age, sex, and smoking habits. Results: Thirteen of 50 subjects were genotype positive, a prevalence of 26%. The most common polymorphisms found in genotype-positive subjects were allele 1.2 for the IL1A gene and allele 1.2 for the IL1B gene. When only subjects older than 30 years were evaluated, the prevalence of genotype-positive individuals was 31%. Conclusion: The prevalence of genotype-positive subjects in a Hispanic population was 26%, similar to the prevalence found among ethnic populations from or descended from Northern, Central, and Southern Europe.