To evaluate the significance of specific IgG and specific IgG4 in the development of work-related respiratory symptoms, specific IgG and specific IgG4 to Black GR-human serum albumin (HSA) conjugate were measured by ELISA in 309 dye-exposed workers and 63 unexposed patients as negative controls. A survey revealed that 78 (25.2%) had work-related lower respiratory symptoms with or without nasal, skin or eye symptoms. Specific IgG and specific IgG4 were detected in 23% and 14% of the exposed workers, respectively. The prevalence of specific IgG and specific IgG4 was significantly higher in smokers and workers with specific IgE or those with lower respiratory symptoms (P < 0.05), but was not associated with work station, duration of dye exposure or atopy. These results suggested that the existence of specific IgG to Black GR HSA might represent a response to Black GR exposure and be closely related with work-related respiratory symptoms.