Caveolins, structural protein coats of caveolae primarily involved in membrane-related functions have, also been found associated to lipid droplets (LD), specialized organelles for fat storage In the present. Study, we wanted to delineate the main features that govern the presence of caveolin-1 on adipocyte lipid droplets. Using either Morphological OF biochemical approaches, we found caveolins to associate to LD in 3T3-L1 adipocytes during their late maturation phase. The time course of this association Could be modulated by constitutive activation of src-kinase, suggesting that the specific enrichment of caveolins in enlarged LD results from an active pathway rather than trapping of caveolins to lipid storage organelle acting as a passive sink. The fat cell size dependence of the association of organized caveolins on adipocytes LD Suggests a role for these proteins in the long-term handling of lipid stores. (C) 2008 Elsevier Inc. All rights reserved.