Serum ferritin, serum iron, total iron-binding capacity (TIBC) and erythrocyte protoporphyrin were measured in a group of 69 children (6.4 +/- 3.6 years) living in a rural area of Mauritania. The predictive value of low serum ferritin was calculated for each iron parameter. A serum ferritin value above 12 micrograms/l was present in 50.2% of children with abnormal serum iron, in 59.0% of those with abnormal TIBC, in 60.3% of those with abnormal transferrin saturation and in 60.0% of those with abnormal erythrocyte protoporphyrin. The percentages varied from 88.0 to 94.8% for a predictive value of serum ferritin of less than 50 micrograms/l. Nearly 35% of children had biochemical evidence of iron deficiency, i.e. 2 abnormal independent iron parameters or more, including serum ferritin of less than 12 micrograms/l. Nearly 32% had probable iron deficiency, i.e. 2 abnormal independent iron parameters, with a serum ferritin value between 13 and 50 micrograms/l.