Model of the Cdc42–Par complex function in the regulation of the apical endocytotic pathway. Our data suggest that Cdc42 and the Par complex cooperate to regulate two distinct steps in the endocytosis of apical membrane components. The Cdc42–Par complex inhibits endocytosis from the plasma membrane and also promotes progression from the early endosome (EE) to the multivesicular body/late endosome (MVB/LE). Apical and basolateral (including AJ) proteins follow distinct endocytotic routes.