This study was a case-control study of 44 children ages 3 to 24 months. The purpose of the study was to compare the humoral and cellular immunity of 29 patients (Group I) who were less than the 3rd percentile for weight by Turkish standards versus a control group of 15 patients (Group II) with weights between the 25th and 90th percentiles. The Group I patients were considered to have protein energy malnutrition (PEM) with various degrees of severity based on a Turkish classification method established by Dogramaci and Wray in 1958. None of the Group I patients had frank kwashiorkor, but 19 had bronchopneumonia, six had gastroenteritis, and four had both forms of infection at the time studies were done. Detailed immunologic evaluation was carried out on all the subjects including IgG, IgM, IgA, C3, mature T lymphocytes (CD3+), helper/inducer T Lymphocytes (CD4+) and suppressor/cytotoxic T lymphocytes (CD8+). The authors chose to study patients with PEM and infections because the immune response is more likely to be suppressed at this time. In the PEM group all of the immunoglobulins (IgG, IgM, IgA) were significantly elevated over the controls level (P < .01). This hyperimmunoglobulinemia state has been previously reported and could be secondary to reduced suppressor T lymphocytes (C8+). C3 complement levels were also significantly lower (P < .01) than controls, which have been previously noted. These low C3 levels could be secondary to decreased production from the liver or increased utilization with an intercurrent infection. In evaluating the lymphocyte series CD3+, CD4+, and CD8+ were all significantly reduced while CD4/CD8 levels were normal.