Cholinesterase inhibitors are currently the mainstream of symptomatic treatment of patients with Alzheimer's disease. The response to treatment with cholinesterase inhibitors is clinically difficult to predict. Several demographic, clinical and biological variables have been proposed as pretreatment predictors of long-term therapy efficacy. In this paper, consistently with previous reports, we confirm that higher initial disease severity and faster progression of cognitive impairment increase the chance of a clinically meaningful response to cholinesterase inhibitor therapy in a carefully selected population of patients with Alzheimer's disease. Moreover, for the first time we demonstrate the association between the increase in the concentration of plasma Abeta(1-42) peptide after 2 weeks of treatment with an initial dose of rivastigmine and the likelihood of a positive response to treatment after 6 months. A change in plasma Abeta(1-42) level might constitute a novel biochemical predictor of rivastigmine treatment efficacy in Alzheimer's disease.