The failure of cholinesterase inhibitors to produce noticeable improvement in about half of patients with Alzheimer's disease (AD) may result from heterogeneity of neurotransmitter abnormalities in this disorder. This study examined whether pretreatment postural blood pressure (BP) drop, which presumably reflects sympathetic response, differed in patients who were responders or nonresponders to the cholinesterase inhibitor, HP 029. Twenty-three AD patients completed a double-blind dose-finding phase of a clinical trial in which four doses of HP 029 and placebo were administered. Evaluation for efficacy occurred after 7 days of treatment at each dose. Of the 23 patients, 12 were classified as responders in the dose-ranging phase of the study. Nonresponders demonstrated significantly greater decreases in pretreatment systolic postural BPs when going from a supine to sitting position than did responders. The greater postural BP drop in nonresponders may identify a subgroup of AD patients that responds poorly to cholinesterase inhibitors.