ADP-ribosylation factor (ARF) 6 has been shown to play a role in vesicular transport; however, the expression and subcellular localization of the endogenous protein have not been clearly delineated. In this study, an ARF6-specific monoclonal antibody was raised and used to examine the subcellular distribution and expression of ARF6 in various tissues and during the differentiation of several well characterized cell types. We found that ARF6 localizes in both the cytosol and membranes of all tissues and cells tested. Moreover, ARF6 in 3T3-L1 adipocytes is principally localized on the plasma membrane, but substantial amounts are detected in the cytosolic and intracellular membrane fractions. We observed an increased expression of ARF6 during the differentiation of B lymphocytes to plasmocytes. However, the expression of ARF6 decreased during adipogenesis and monocyte differentiation. In contrast, the expression of other ARFs, detected by the monoclonal antibody 1D9, did not significantly change during differentiation of the aforementioned cell types. Taken together, our results indicate that ARF6 is a broadly expressed, differentially regulated GTPase that is present in cytoplasm and on both cell-surface and intracellular membranes and whose functions may include tissue-specific effects on vesicular trafficking during cellular differentiation.