In the present report we show the gene expression pattern of VIP and VIP1 receptor in two peritoneal cell populations, macrophages and lymphocytes by reverse transcription (RT) and polymerase chain reaction (PCR). Only in the lymphoid cells we have obtained a specific VIP cDNA product of 458 bp identical in size to the one obtained from cerebral cortex. On the other hand, we have obtained in both peritoneal populations lymphocytes and macrophages, a specific VIP1 receptor cDNA product of 311 bp identical in size to that obtained from lung. These results have been confirmed by Southern blot hybridization. Our findings suggest an autocrine/paracrine action of VIP in peritoneal microenvironment, supporting an immunoregulatory role for this neuropeptide.