This study demonstrated a mediation effect in serial learning. Prior to learning an A-B-C-D serial list Experimental Ss learned an A-B’, C-D’ paired-associate (PA) list in which B and D were the primary word associates of B’ and D’. A Control group learned an A-X, C-Y PA list and then the same serial list. Serial learning was superior in the Experimental condition. It was suggested that the serial learning was mediated by an A-B’-B sequence in which A elicited B’ and B’, in turn, evoked its primary associate B.