Previous work has shown that malnutrition has deleterious effects on both IQ and aspects of temperament. It is hypothesized that while malnutrition bears a direct relation to IQ, aspects of temperament are also involved in a mediating role so that they produce indirect associations between malnutrition and IQ. The study examines the association of 3 indices of malnutrition--stunting, anemia and wasting--to Verbal IQ (VIQ) and Performance IQ (PIQ) and temperament in 1,376 3-year-old and 11-year-old children in Mauritius. Two dimensions of temperament were extracted from ratings of behavior and were labeled as Uninhibited (UI) and Task Orientation (TO). At age 3 stunting had direct relations to Verbal IQ and Performance IQ and also indirect relations via the mediating effect of temperament (UI but not TO). In the case of anemia there were no direct relations to VIQ or PIQ but both temperament mediators were involved in indirect relations. For wasting, indirect but not direct relations were observed. When age 11 cognitive performance was examined, there were direct relations to stunting and anemia and indirect relations via UI, but not TO. The relations between malnutrition and IQ were graded and linear showing that it is not only when malnutrition is defined by its severest levels that it has an effect on cognitive performance. It is suggested that malnutrition affects those brain structures and functions that are involved in both cognitive behavior and temperament.