36 undergraduates were given lists of 8 items (4 digits and 4 letters) presented at .75 sec/item with ordered recall instructions. Ss were either to copy the items as presented and then recall or to recall the items without prior copying. Recall after copying was slightly worse than recall without copying (p < .05). In both conditions, intrusions among letters and between letters and numbers tended to follow acoustic similarity (p < .001). Vowel similarities were more important than consonant similarities, but both effects were significant (p < .0001). There was a correlation of .58 between the number of letters similar to a presented letter and the frequency with which that letter was forgotten (p < .01). Short-term memory appears to use an auditory or speech-motor code. (PsycINFO Database Record (c) 2006 APA, all rights reserved)