In a series of three studies, we evaluated simulated data with reversal designs to determine whether partial-interval recording (PIR) and momentary time sampling (MTS) detected changes that were evident with continuous measures. The results from Study 1 showed that MTS with interval sizes up to 30 s detected most of the moderate and large changes in duration events and MTS with interval sizes up to 1 min detected most large changes in duration events. By comparison, PIR with 10-s intervals detected approximately half of all changes in duration events. The results of Study 2 showed that only 10-s PIR reliably detected most small, moderate, and large changes in frequency events. The results of Study 3 showed that PIR with 10-s intervals generated a relatively high percentage of false positives for duration events, whereas MTS did not. As a whole, the results support previous findings, but also provide new guidelines for the use of PIR and MTS. Copyright © 2008 John Wiley & Sons, Ltd.