Technical Abstract: Ferrous fumarate is a common, inexpensive iron form increasingly used instead of ferrous sulfate as a food iron supplement. However, few data exist as to whether juices enhance iron absorption from ferrous fumarate. We studied 21 children, ages 4.0 to 7.9 years using a randomized crossover design. Subjects consumed a small meal including a muffin containing 4 mg 57Fe as ferrous fumarate and either apple (no ascorbic acid) or orange juice (25 mg ascorbic acid). They were separately given a reference dose of 58Fe (ferrous sulfate) with ascorbic acid. Iron absorption increased from 5.5 +/- 0.7% to 8.2 +/- 1.2%, P<0.001 from the muffins given with orange juice compared with muffins given with apple juice. The absorption of ferrous fumarate given with orange juice and enhancement of absorption by the presence of juice were significantly positively related to height, weight, and age, (P<0.01 for each). Although iron absorption from ferrous fumarate given with apple juice was significantly inversely associated with the (log transformed) serum ferritin, the difference in absorption between juice types was not (P>0.9). These data demonstrate an overall benefit to iron absorption from ferrous fumarate provided with orange juice. The effect was age related such that in children >6 years of age, there was a nearly 2-fold increase in iron absorption from ferrous fumarate given with orange juice.