Previous studies found advance instruction regarding the final recall trial reduced retroactive inhibition in serial learning (3) and paired-associate learning (4) but not in free recall (2). Postman and Stark (4) suggested instructed subjects rehearsed List 1 during List 2 acquisition. Decker's (2) negative finding may have been due to rehearsal of List 1 by uninstructed as well as instructed subjects. This experiment included groups instructed to forget List I to minimize rehearsal. List 1 rehearsal may impair Lisc 2 acquisirion. If s3, the forget instruction should yield superior List 2 performance. Since Decker's (2) lists consisted of words from the same categories. List 1 rehearsal may not have impaired List 2 acquisition due to common category labels and/or interitem associations. When lists containing different categories are rehearsed simultaneously there may be a more adverse effect on both lists. Subjects were instructed to remember List 1 while learning List 2, instructed to forget List 1, or given List 2 instructions containing no mention of List 1. Instruction was factorially combined with category type, same or different. Twenty university students served as subjects in each group. Booklecs contained instruction, study, recall, and filler pages. Each list consisted of 36 nouns, six from each of six categories (1). There were two study-test trials with a 2-min. study period and a 90-sec. recall interval on each list. The interlist interval was 1 min. A 3-min. recall trial immediately followed List 2 acquisition. Groups instructed to forget List 1 recalled List 2 while all ochers recalled List 1. List 2 acquisition by the different categories groups (M = 43.13, SD = 8.04) exceeded that of the same categories groups (M = 38.60, SD = 8.88; K.nt = 8.48, fi < ,005 ). Lisc 1 recall by the different categories groups (A1 = 18.90, SD = 7.71 ) was