The majority of patients infected with lymphatic filariae are microfilaremic but tend to manifest little obvious pathology because of the infections. Data collected from the Mongolian gerbil–Brugia spp. model for human lymphatic filariasis suggest this experimental animal model system most closely represents this patient group and will be useful in studying immunological parameters associated with chronic infections. This article reports the quantitation of interleukin (IL)-4, IL-5, IL-10, IL-13, and interferon (IFN)-γ messenger RNA (mRNA) in gerbils after a primary subcutaneous infection with Brugia pahangi. Chronically infected gerbils showed elevated IL-4 in all tissues, compared with earlier time points, linking this Th2 cytokine to the downregulation of responsiveness, which develops in gerbils and humans. Both IL-5 and IL-13 mRNA expression were transient in all tissues. The peak in IL-5 at 14–28 days postinfection reflects the peak of peripheral eosinophilia observed in B. pahangi–infected gerbils. Little IFN-γ mRNA was reported from chronically infected gerbils. The data collected thus far suggest that the expression profile of many of the measured cytokines in B. pahangi–infected gerbils reflects what is seen in an important subset of humans infected with lymphatic filariae, the microfilaremic, asymptomatic patient.