The effect of faba bean hull fibre on utilization of Fe, Zn and Cu was studied. The degree of binding these elements by the hull fibre was measured in vitro and their retention was determined in rats fed on diets without hulls (control) or with hulls either extracted with acetone to remove phenolic compounds (He) or extracted and incubated in a solution of sulphates of the elements under study (Hi). Incubation performed in vitro in conditions simulating those in the digestive tract (37°C, pH 2 for 5 h followed by pH 5 for 1 h) increased Fe, Zn and Cu content in the hulls by 36.6, 22.4 and 5.4 mg/100 g, respectively. The amount of fibre-bound elements in the experimental Hi diet corresponded to 40% of the amount provided by the control diet. In the animals fed during 4 weeks on the control and experimental diets the total body Zn content was similar in all groups (4.5-4.6 mg/rat). The Fe and Cu content was smaller both in the rats receiving extracted and incubated hulls as compared with control animals (8.26 and 7.58 vs 8.59 and 0.51 and 0.48 vs 0.55 mg/rat, respectively). Small differences between the groups seem to indicate that in spite of the high sorption capacity of faba bean hull fibre in vitro, its effect on utilization of Fe, Zn and Cu in vivo was relatively small.