106 consecutive patients with Alzheimer's disease living in the community were examined in a memory clinic from a neurological department. They were screened for weight loss over the last 2 years. Age, duration of the disease, behavioral disorders, mini mental status examination, body mass index were recorded. Tumor necrosis factor alpha (TNFalpha), interleukin-1beta (IL-1beta), interleukin 6 (IL-6) and interleukin 2 (IL-2) blood levels were measured. Weight loss was reported in 42.5% of the patients. TNFalpha levels were significantly higher in these patients (18.8 versus 15.8 pg/mL; p=0.04) than in patients without weight loss. Weight loss was also associated with a lower MMSE score (16.9 versus 19.3; p=0.03), current pacing (20% versus 1.6%; p=0.002), and hallucinations (20.0% versus 3.3%; p=0.008). The levels of the other cytokines did not differ between the patients with and without weight loss. Our findings suggest an association between high levels of circulating TNFalpha and unexplained weight loss in Alzheimer's disease.