1. This investigation included three experiments to determine whether the iron content of egg yolks could be enriched by supplementation of the laying diet with iron bound to organic compounds (Experiment 1), serine and methyl group donors methionine and choline (Experiment 2) or phytoestrogens (Experiment 3). 2. Hens at 34, 54 and 56 weeks of age were given experimental diets for 6, 4 and 4 weeks, respectively, in Experiments 1-3. Yolks from eggs laid over three successive days in the final week of feeding were pooled for each hen for analysis of iron by inductively coupled plasma mass spectrometry. 3. Iron concentration in egg yolk averaged 68-70, 66-71 and 62-69 mu g/g in the respective experiments. 4. The addition of bloodmeal (1 center dot 22 mg Fe/egg) or phytoestrogens (1 center dot 25 mg Fe/egg) increased the total iron content of yolks by over 15% compared with the control diet (1 center dot 10 mg Fe/egg), and although this increase was not statistically significant it suggests that the iron content of eggs could be sufficiently manipulated to justify a nutritional claim of iron enrichment.