Disturbed copper (Cu) homeostasis may be associated with the pathological processes in Alzheimer's disease (AD). In the present report, we evaluated the efficacy of oral Cu supplementation in the treatment of AD in a prospective, randomized, double-blind, placebo-controlled phase 2 clinical trial in patients with mild AD for 12 months. Sixty-eight subjects were randomized. The treatment was well-tolerated. There were however no significant differences in primary outcome measures (Alzheimer's Disease Assessment Scale, Cognitive subscale, Mini Mental Status Examination) between the verum [Cu-(II)-orotate-dihydrate; 8 mg Cu daily] and the placebo group. Despite a number of findings supporting the hypothesis of environmental Cu modulating AD, our results demonstrate that oral Cu intake has neither a detrimental nor a promoting effect on the progression of AD.