Caveolin-1 (Cav1) is expressed in the basolateral membrane domain of renal collecting duct (CD) principal cells (PCs), where it is associated with caveolae. To reveal any potential involvement of Cav1 in vasopressin signaling, we used specific mono- and polyclonal antibodies to examine its localization in CD PCs of Brattleboro (BB) rats treated with vasopressin (DDAVP). Compared to controls, immunofluorescence revealed a time-dependent increase in Cav1 expression in the apical membrane domain of PCs, where it overlapped with aquaporin-2 (AQP2). After 24 h of DDAVP treatment, Cav1 was visible as an increased number of small apical spots. The staining gradually became more extensive and after 2 weeks of DDAVP it occupied a majority of the apical membrane domain of many PCs. Cav1 also assumed an apical localization in PCs of DDAVP-treated Sprague-Dawley (SD) and Long-Evans (LE) rats. Similarly, Cav2 appeared at the apical pole of PCs following DDAVP treatment of BB, SD, and LE rats. Immunogold electron microscopy confirmed bipolar Cav1 membrane expression in DDAVP-treated BB rats, while caveolae were only detected on the basolateral membrane. Immunoblotting of BB rat whole kidney homogenates revealed no significant increase in Cav1 levels in DDAVP-treated rats, suggesting that DDAVP induces Cav1 relocalization or modifies its targeting. We conclude that Cav1 and Cav2 trafficking and membrane localization are dramatically altered by the action of DDAVP. Importantly, the absence of apical caveolae indicates that while caveolins may have an as yet undetermined role in vasopressin-regulated signaling processes, this is probably unrelated to AQP2 internalization by caveolae.