Some studies suggest a decrease in interferon (IFN) gamma production among atopic individuals, and others refer to low IFN-gamma levels as a characteristic of asthma, regardless of the atopic state. Recent research has indicated a relation between asthma and a tendency toward a bacille Calmette-Guerin (BCG) vaccine scar with a small diameter, suggesting an association of this illness with the low production of IFN-gamma. The aim of this study was to check the hypothesis that asthmatic patients with a small BCG scar present low IFN-gamma production. This work was a quasi-experimental study. The capacity to produce IFN-gamma among 12 asthmatic patients with an average BCG vaccine scar diameter <5 mm was compared with 7 nonasthmatic individuals with scars > or =5 mm using whole blood cells stimulated by purified protein derivative (PPD), phorbol myristate acetatelionomycin (PMA/Iono) and medium (no stimulus). The study also analyzed the relation between IFN-gamma production after PPD stimulation and eosinophil count, total IgE, and dust-mite-specific IgE levels. The asthmatic patients presented a decrease in IFN-gamma production in comparison with a control group after PPD stimulation (p < 0.02). However, the same was not observed when PMA/Iono stimulation was used or when no stimulation was used. Asthmatic patients with small BCG scars showed a decrease in IFN-gamma production, suggesting that there may be an intrinsic characteristic of these patients.