Chemoattractant receptors on leukocytes initiate migratory and cytotoxic activities via GTP-binding proteins. Recent cloning of cDNA encoding the formylpeptide receptor indicates it to be a member of the class of seven membrane spanning domain receptors which couple to G proteins. Leukocyte activation by chemoattractants requires sequential metabolic pathways involving phospholipase C then phospholipase D. Interestingly, the formylpeptide receptor physically associates with both a heterotrimeric G protein and a low molecular mass GTP-binding protein. These multiple GTP-binding proteins may regulate the function of chemoattractant receptors.