We studied the effects of iron deficiency on the in vivo absorption (by using the intestinal perfusion technique in the duodenum) of different dietary sources of iron (haem, non-haem and equal parts of both forms) and investigated the interactions between iron and calcium, phosphorous, magnesium, copper and zinc in control and iron-deficient rats. Three perfusion solutions containing a different source of iron were used: solution 1, ferric citrate; solution 2, haemoglobin; solution 3, equal parts of ferric citrate and haemoglobin. We also tested the same perfusion solution with 2,4-dinitrophenol (2,4-DNP), an inhibitor or oxidative phosphorylation (solutions 1-I, 2-I and 3-I). In control rats we observed three mechanisms of iron absorption: passive for soluble iron salts, active receptor-mediated for non-haem iron complexes, and active receptor-mediated for haem iron. In anaemic rats iron absorption was greater than in controls, except after perfusion with solution 2 (containing haemoglobin). Absorption increased as a result of both the passive and active, receptor-mediated mechanism for non-haem iron complexes. The active component was influenced by the depletion of haem receptors under severe iron deficiency. The absorption of calcium, copper and zinc in iron-deficient animals was lower than in controls, whereas phosphorus and magnesium absorption were not significantly affected. After perfusion with solution 2 or 3, calcium, copper and zinc absorption were lower than after solution 1. We conclude that ferropoenic anaemia in the rat impairs the absorptive process of those minerals that are absorbed, at the duodenal level mainly via active transport (haem iron, calcium, copper and zinc), but does not affect the active component involved in non-haem iron absorption.