OBJECTIVES: To compare the efficacy, safety and tolerability of a novel rivastigmine transdermal patch with conventional rivastigmine capsules and placebo in patients with Alzheimer's disease (AD). METHODS: In this 24-week, multicenter, double-blind, double-dummy, placebo- and active-controlled trial, patients with probable AD were randomized to one of four treatment groups: 12 mg/day rivastigmine capsules; 10 cm2 (9.5 mg/24 h) rivastigmine patch; 20 cm(2) (17.4 mg/24 h) rivastigmine patch; or placebo. Primary efficacy measures were the Alzheimer's Disease Assessment Scale-Cognitive subscale (ADAS-Cog) and Alzheimer's Disease Cooperative Study--Clinical Global Impression of Change (ADCS-CGIC). RESULTS: One thousand one hundred and ninety five AD patients from 21 countries participated in the study. Treatment differences (vs placebo) on the ADAS-Cog at Week 24 in 10 cm2 patch, 20 cm2 patch and capsule groups were 1.6 (p=0.005), 2.6 (p<0.001) and 1.6 (p=0.003). Treatment differences on the ADCS-CGIC were 0.3 (p=0.01), 0.2 (p=0.054) and 0.3 (p=0.009). Comparison between the 10 cm2 patch and the capsule revealed non-inferiority. Rates of nausea in the 10 cm2 patch and capsule groups were 7.2% and 23.1%, respectively; rates of vomiting were 6.2% and 17.0%, respectively. Moderate or severe skin irritation occurred in<or=10% patients across the four patch sizes (5, 10, 15 and 20 cm2). CONCLUSIONS: The target dose of 10 cm2 rivastigmine patch provides efficacy similar to the highest doses of capsules with a superior tolerability profile. The transdermal patch with rivastigmine may offer convenience important to many caregivers and patients. Copyright (c) 2007 John Wiley & Sons, Ltd.