The hypothesis that retention differences between semantic and phonemic encodings are in part attributable to greater distinctiveness of semantic encodings was investigated in two experiments. The memory-enhancing effects of instructions designed to increase trace distinctiveness were much greater with phonemic than with semantic processing. The usual inverse relationship between word frequency and recognition was reduced by instructions designed to increase trace distinctiveness, suggesting that the customary advantage of rare over common words may be partially due to greater encoded distinctiveness of rare words.