Evaluated the validity of D. Rundus and R. C. Atkinson's overt rehearsal technique in a study with 40 undergraduates. To assess any changes in input processing which might result from overt rehearsal, S-paced item presentation was employed that yielded a measure of study time at successive input positions. This measure monitors S's activity during the stage of processing that might be affected by overt rehearsal and is therefore more appropriate to the problem than a recall performance measure. A covert rehearsal control group was included, which enabled an evaluation of the effects of externalized rehearsal. It was shown that overt rehearsal disrupts the cognitive activities normally utilized on standard memory tasks. In particular, overt rehearsal increased the amount of serial processing and required greater study time relative to covert rehearsal. These results are discussed in terms of a depth-of-processing framework. (PsycINFO Database Record (c) 2006 APA, all rights reserved). © 1975 American Psychological Association.