We retrospectively identified 136 patients with abdominal aortic aneurysms (AAAs) who were initially evaluated as outpatients. Twenty-seven of these patients met the following criteria for eligibility in the study: (1) roentgenographic documentation of an AAA larger than 3 cm, (2) at least two serial ultrasound size determinations over a minimum six-month interval, and (3) a documented medication history. Of these 27 patients, 12 received long-term beta-blockade, while 15 received no beta-blockade. The two groups were comparable with respect to age, sex, initial aneurysm size, mean systolic and diastolic blood pressure, and duration of follow-up (mean, 34 months). Among patients with beta-blockade, the mean growth rate was 0.17 cm/y. The rate for the controls was 0.44 cm/y. One patient of 12 (8%) in the beta-blocker group had a rate that exceeded the mean for the overall group compared with eight patients of 15 (53%) in the group with no beta-blockade. This difference was statistically significant. Thus, beta-blockade may be associated with a decreased AAA growth rate in this small, retrospective study.