Cell interactions with extracellular matrices play important roles in morphogenetic processes during embryonic development. Extracellular matrix receptors of the integrin family have been implicated in these steps. Recent studies indicate that a variety of integrins can be differentially expressed during development, consistent with diverse roles for integrins in embryogenesis. The present study compares the expression patterns of several major members of the alpha V integrin subfamily, focusing on mRNA expression of alpha V, beta 1, beta 3, and beta 5 subunits during mouse embryonic organogenesis using Northern blot analysis and in situ hybridization. The alpha V and beta 1 subunits showed widespread tissue expression, although most tissues expressed alpha V at relatively low or basal levels. The mRNA for beta 5 was also expressed in a variety of embryonic organs and showed unusual localization patterns in certain organs. Striking, high-level expression of beta 5 transcripts was detected in the ependymal layer of the central nervous system, glomeruli of the kidney, epicardial region of the heart, and in the tooth germs, suggesting specific functions for this molecule during morphogenetic events in these organs. In contrast, few beta 3 transcripts were expressed during mid-gestation mouse embryogenesis except in megakaryocytes within the embryonic liver. These observations of differing expression spectra suggest that members of the alpha V integrin subfamily have distinct roles and also suggests that they have different transcriptional regulation. The beta 5 integrin is unique in its degree of tissue-specific mRNA regulation associated with morphogenesis of embryonic organs.