AbstractLysophospholipids (LPs) such as lysophosphatidic acid (LPA) and sphingosine‐1‐phosphate (S1P) are known to mediate various biological responses, including cell proliferation, migration, and differentiation. To better understand the role of these lipids in mammalian early development, we applied whole‐mount in situ hybridization techniques to E8.5 to E12.5 mouse embryos. We determined the expression patterns of the following LP receptor genes, which belong to the G protein–coupled receptor (GPCR) family: EDG1 to EDG8 (S1P1 to S1P5 and LPA1 to LPA3), LPA4 (GPR23 /P2Y9), and LPA5 (GPR92). We found that the S1P/LPA receptor genes exhibit overlapping expression patterns in a variety of organ primordia, including the developing brain and cardiovascular system, presomitic mesoderm and somites, branchial arches, and limb buds. These results suggest that multiple receptor systems for LPA/S1P lysophospholipids may be functioning during organogenesis. Developmental Dynamics 237:3280–3294, 2008. © 2008 Wiley‐Liss, Inc.