Agonist activation of a subset of G protein coupled receptors (GPCRs) stimulates cell proliferation, mimicking the better known effects of tyrosine kinase growth factors. Cell survival or apoptosis is also regulated via pathways initiated by stimulation of these same GPCRs. This review focuses on aspects of signaling by the lysophospholipid mediators, lysophosphatidic acid (LPA), and sphingosine 1 phosphate (S1P), which make these agonists uniquely capable of modulating cell growth and survival. The general features of GPCR coupling to specific G proteins, downstream effectors and signaling cascades are first reviewed. GPCR coupling to G_i and Ras/MAPK or to G_q and phospholipase generated second messengers are insufficient to regulate cell proliferation while G_12/13/Rho engagement provides additional complementary signals required for cell proliferation. Survival is best predicted by coupling to G_i pathways that regulate PI3K and Akt, but other signals generated through different G protein pathways are also implicated. The unique ability of LPA and S1P to concomitantly stimulate G_i, G_q, and G_12/13 pathways, given the proper complement of expressed LPA or S1P receptors, allows these receptors to support cell survival and proliferation. In pathophysiological situations, e.g., vascular disease, cancer, brain injury, and inflammation, components of the signaling cascade downstream of lysophospholipid receptors, in particular those involving Ras or Rho, may be altered. In addition, up or downregulation of LPA or S1P receptor subtypes, altering their ratio, and increased availability of the lysophospholipid ligands at sites of injury or inflammation, likely contribute to disease and may be important targets for therapeutic intervention. © 2004 Wiley‐Liss, Inc.