A list of words that occur frequently in everyday language is more recallable than a list of words that occur only rarely. This "word frequency" effect is eliminated, or even reversed slightly, if the common and rare words are mixed together in the same list. This pattern of results is replicated in Experiment 1. The remaining experiments evaluated the hypothesis that the interaction between type of list and word frequency is the result of subjects focusing on the low frequency words during study of the mixed lists. The hypothesis received limited support when a differential-attention strategy was made less likely by requiring that an orienting task be performed during presentation of the list (Experiment 2) and strong support when such a strategy was made even less likely by presenting the words in an incidental memory procedure (Experiments 3 and 4). In the latter case, the high frequency words held no more of a recall advantage over the low frequency words when frequency was varied between lists than when it was varied within lists.