To study the topological relationship between the ribosomal protein S19 (RP S19) and C5a receptor genes were objective. Fluorescent in situ hybridization analyzes (FISH) were performed in guinea pig metaphase lymphocytes. The signals denoting the RP S19 gene and the C5a receptor gene completely overlapped each other. The RP S19 and C5a receptor genes co-localized on the same chromosome.