On each trial after presentation of eight two digit numbers followed by eight two syllable words, forty-eight female subjects were cued to recall (1) numbers only, N-, (2) numbers then words, NW, (3) words then numbers, WN, or (4) numbers then perform a word association task, NWA. A decrement was obtained in numbers list recall in the NW condition as compared to recall in the N- condition. This finding replicated the results of earlier studies by Epstein (1969b and 1970) which assumed the decrement to be caused by mnemonic processing of the word lists. A similar decrement was obtained in the NWA condition. Since the demands on mnemonic processing of the word lists are identical in the NWA and N- conditions, the observed decrement in number list recall in the NWA condition clearly demonstrates a source of recall interference which differs from retention processing. Furthermore, this source of interference may have been contributory to the decrement in the NW condition since NW shares with the NWA condition the requirement that a task be performed subsequent to recall. The results are interpreted as suggesting that the source of interference associated with delayed performance of a task may be due to differential cue processing difficulty.