The extent of type 2 cytokine gene expression in patients with pulmonary tuberculosis (TB) was studied by use of quantitative nested reverse-transcription polymerase chain reaction on freshly isolated peripheral blood mononuclear cells. Interleukin (IL)-4 and IL-13 mRNA expression was significantly greater in patients-median mRNA copy numbers were 1.7 and 1.1 log10 higher, respectively-than in matched tuberculin-positive control subjects. Significant correlations with radiologic extent of disease and serum IgE levels supported the biologic significance of these results. Interferon-gamma mRNA copy numbers exceeded those of type 2 cytokines but were only marginally lower in patients than in control subjects. Gene expression of an IL-4 splice variant (IL-4delta2) was bimodally distributed in both patient and control groups. Patients with greater IL-4delta2 expression also expressed more IL-4 mRNA and had more extensive disease. Type 2 cytokines are associated with immunopathologic changes in TB patients but could be a cause or consequence of disease.