Asthma is a condition characterised by a chronic immunoinflammatory response to different triggers. Neopterin (NPT) is synthesised by human macrophages upon stimulation with interferon-gamma and is also capable of enhancing the oxidative potential of reactive oxygen species. NPT is useful for the monitoring of cell-mediated (Th1-type) immune activation. This study analysed the behaviour of NPT in long lasting asthma, considering its role as a marker of Th1 environment. Allergic parameters (skin prick tests, Immunoglobin E (IgE), and eosinophil count) and NPT were evaluated in an asthmatic group and in a control group. We also analysed the C Reactive Protein (CRP) concentration, Total Antioxidant Status (TAS) and Superoxide Dismutase Enzyme (SOD) in both groups. A group of individuals aged over 65 years old was selected. It included 64 asthmatic patients (72+/-5 years) and 41 healthy individuals (79+/-7 years). Blood cell counts showed statistically different median values of eosinophils (5.42+/-4.7 vs 2.8+/-2.8;p<.04), IgE (493.2+/-549.8 vs 85.3+/-194.UI/ml; p=.000) and NPT was non-statistically decreased (2.4+/-2.8 vs 4.0+/-4.7 ng/ml) in allergic asthmatic patients when compared with non-allergic asthmatic patients. Both allergic and non-allergic asthmatic patients presented a statistically significant decreased expression of TAS (0.84+/-0.14/0.86+/-0.11 vs 0.91+/-0.10 mM) and SOD (584.8+/-108.7/595.6+/-235.9 vs 822.9+/-179.5) when compared with normal control subjects. Our results suggest macrophage involvement in asthma pathogenesis. The deficit in antioxidant defence impacts negatively on this disease. The increase of NPT values in non-allergic asthma consolidates these affirmations and mapping this parameter should be part of the work of an analytical study panel as it may lead to allergic asthma being distinguished from non- allergic asthma.