We previously reported that angiotensin converting enzyme inhibitors (ACEIs) decrease the rate of cognitive decline in elderly patients with hypertension, but their impact on patients with Alzheimer's disease (AD) is not known. A total of 62 elderly patients with AD were enrolled, and 52 completed the study for 6 months. Mini-Mental Status Examination (MMSE), Clock Draw Test (CDT), working memory (Digit Ordering), Instrumental Activities of Daily Living (IADL) scale, and the Screen for Caregiver Burden (SCB) were collected at baseline, 3 months, and 6 months. AD patients receiving ACEI (N = 15) demonstrated a slower rate of decline in digit forward (P = .003) and IADL scale (P = .003) and an improved measure of caregiver burden (P = .04) but not MMSE (P =.15) or CDT (P =.9) compared with those not receiving ACEI after adjusting for other risk factors. This study suggests that use of ACEI in AD patients is associated with slower rate of AD progression. A randomized clinical trial is needed to confirm our finding.