Two integral membrane proteins, influenza virus hemagglutinin (HA) and vesicular stomatitis virus G protein, are transported to and accumulated on the apical and basolateral surfaces, respectively, of the plasma membrane of polarized epithelial cells. We have used chimeric constructions to identify the domains of HA and G proteins which contain the signals for polarized transport. Previously, we have shown that a chimeric protein containing the cleavable leader and the ectodomain of HA fused to the anchoring and cytoplasmic domains of G is transported to the apical surface of polarized MDCK cells (McQueen, N.L., Nayak, D.P., Stephens, E.B., and Compans, R.W. (1986) Proc. Natl. Acad. Sci. U.S.A. 83, 9318-9322). In this report we show that a chimera containing the cleavable leader and ectodomain of G fused to the anchoring and cytoplasmic domains of HA is transported to the basolateral surface of polarized cells. Another chimera which contains the leader sequence of G fused to leader minus HA is transported to the apical surface of polarized cells. These results taken together suggest that the signals for the polarized transport of HA and G proteins may reside in their ectodomains.