To clarify the effect of indoor air pollutants on nerve growth factor (NGF) production in lung, male C3H/HeN mice were exposed to filtered air (control) or toluene at levels of 0.9ppm, 9ppm, or 90ppm for 30min via nose-only inhalation on days 0, 1, 2, 7, 14, 21, 28, 35, 42, 49 and 56. As an allergic mouse model, some mice (n=24) were immunized with ovalbumin. Lungs from each mouse were collected to determine NGF and related receptor expressions using real-time reverse transcription polymerase chain reaction (RT-PCR) analysis. NGF and TrkA mRNAs were increased in the lungs of the immunized mice following exposure to 9ppm toluene (n=6) (P<0.05ppm vs. 0ppm). Remarkably increased NGF-positive bronchiolus and alveolar epithelium cells were observed in 9ppm toluene-exposed, immunized mice. To determine NGF mediating signaling, we also examined mRNA expression of neurotrophin receptor p75 (p75NTR) and oxidative stress marker, heme oxygenase (HO)-1 in the lung. There is no difference in the expressions of p75NTR and HO-1 between toluene-exposed and control mice. The expression of CCL2 and CCL3 mRNAs was significantly elevated in 9ppm toluene-exposed, immunized mice. These findings suggest that the exposure with volatile organic compounds enhanced NGF expression and airway inflammation stronger in allergic individuals than in healthy individuals.