We investigated the targeting of the V-1a receptor fused with the green fluorescence protein (V1aR-GFP) in polarized MDCK cells. Cells expressing V1aR-GFP displayed binding to vasopressin (AVP) and AVP-induced calcium responses, similar to cells expressing the wild-type V1a receptor. Interestingly, as with the wild-type V1aR, V1aR-GFP is preferentially distributed in the basolateral side of MDCK cells as monitored by confocal microscopy. Furthermore, AVP induced internalization of GFP-tagged receptors. Therefore, the GFP-tagged V-1a receptor retains all the sorting signals of the wild-type receptor and offers an excellent system to elucidate the mechanisms of cell trafficking of V-1a receptors.