In a retrospective comparison of two worker cohorts with elevated total antibody against trimellitic anhydride (TMA) conjugated to human serum albumin (TM-HSA), IgG subclass antibodies against TMA were studied in 19 workers with and 12 workers without TMA-induced immunologic lung disease. The main outcome measures were ELISA index of IgG1, IgG2, IgG3, and IgG4 against TM-HSA. There were no statistically significant differences in levels of any IgG subclass between these two groups. Neither were there any statistically significant differences when workers without lung disease were compared with subgroups of workers with lung disease, such as late respiratory systemic syndrome (n = 8), asthma/rhinitis (n = 6), or both (n = 5). In TMA workers with elevated total antibody against TM-HSA, IgG subclasses against TM-HSA in workers with TMA-induced immunologic lung disease were not different from workers without disease.