While an association between severe protein-energy malnutrition and diminished cellular immunity has been documented, the impact of lesser grades of malnutrition on cellular immunosuppression is less clear. This study emphasizes that the relationship between mild-to- moderate malnutrition and cellular immune function, assessed through delayed-type hypersensitivity testing, is often obscured by the immunosuppressive effects of concurrent infection. Results from an 18-month prospective field study of nutritional status, cellular immune function and morbidity among 62 nomadic Turkana children ages 8 months to 10 years were used to quantify the immunosuppressive effects of mild-to-moderate malnutrition and infection. When controlling for infection at the time of DTH testing, children below -2 s.d. of the reference median weight- for-height or weight-for-age were at least 3 times as likely to be anergic (non-responsive) as children at the reference median. At the same time, infected children experienced a 4.9 times higher risk of being anergic compared to uninfected children. These findings suggest that mild-to-moderate malnutrition and infection are significant independent risk factors for impaired cellular immune function among Turkana children. Am. J. Hum. Biol. 9:381-390, 1997. ยฉ 1997 Wiley-Liss, Inc.