The present study explored several different procedures for determining the amount of change that occurred on the Mini-Mental State Exam [MMSE; Folstein, M. F., Folstein, S. E., & McHugh, P. R. (1975). "Mini-Mental State": A practical method for grading the cognitive state of patients for the clinician. Journal of Psychiatric Research, 12, 189-198] and Modified Mini-Mental State Exam [3MS; Teng, E. L., & Chui, H. C. (1987). The Modified Mini-Mental State (3MS) examination. Journal of Clinical Psychiatry, 48, 314-318] over short and extended test-retest intervals. The test-retest scores were drawn from a selected sample of elderly individuals who participated in the Canadian Study of Health and Aging [Canadian Study of Health and Aging. (1994). The Canadian study of health and aging: Study methods and prevalence of dementia. Canadian Medical Association Journal, 150, 899-913] and were tested on two occasions (CSHA-1 and CSHA-2) separated by 5 years. On each occasion the MMSE and 3MS were administered twice at approximately 3-month intervals. Thus, the mental status tests were administered four times: times 1 and 2 at CSHA-1 and times 3 and 4 at CSHA-2. Mean difference scores and percent of baseline scores showed relatively small group changes over both short and long test-retest intervals for the MMSE and the 3MS. A reliable change index based on a linear regression model controlled for practice effects, psychometric errors due to low reliability, regression to the mean, and accounted for the effects of various demographic variables. Consequently, this reliable change index provided a better estimate of the amount of change that occurred for individual participants than did the mean Retest-Test 1 difference, percent of baseline change, or a reliable change index based on a Retest-Test 1 difference score. Normative data for the change scores are provided.