In this study, we examined the effects of interference and repeated retention tests by comparing groups that performed (a) one or two tests, or (b) two tests separated by interpolated tasks. The task involved pressing five keys in 925 ms. Constant error increased after Block 1 of the second test for the group completing the interpolated tasks. Variable error decreased across retention tests and was smaller for the two-test groups compared to the one-test control. Results differed from previous reports of degraded timing accuracy (Magnuson, Shea, & Fairbrother, 2004), suggesting the present results may have been related to highly accurate performance during the first retention test that reflected successful initial encoding of task information. (Contains 3 notes, 3 figures and 1 table.)