The aim of the present study is to evaluate the relationship between the alpha tumor necrosis factor (TNF-alpha), interleukin 1 beta (IL-1 beta) and the neurological disease associated to the HIV-1 infection and different neurological manifestations (15 infections of the CNS and 11 AIDS-dementia complexes) and 14 from a control group. The mean value of TNF-alpha in CSF of patients with HIV-1 infection and AIDS-dementia complex was 19.8 +/- 30.6 pg/ml, superior to that of the control group (p < 0.05). The group of patients with HIV-1 and opportunistic CNS infection has a TNF-alpha value of 28.5 +/- 37.8 pg/ml, that is superior to that of the patients with the AIDS-dementia complex (TNF-alpha = 7.9 +/- 9.4 pg ml; p < 0.05). Within the group of patients with a CNS infection, the value of TNF-alpha was greater in those in the acute phase (44.2 +/- 42.4 pg/ml) than in those in the chronic phase (6.8 +/- 7.6 pg/ml; p < 0.05). The TNF-alpha in the CSF is a good marker of infection of the CNS in the HIV-1 infection.