The average iron level in the blood plasma of six gilts, weighting between 120 kg and 130 kg, was 103. 3 micrograms/100 ml, prior to early-morning feeding. The iron fixation capacity, measured at the time, was 673 micrograms/100 ml. Average iron levels went up to 121.3 micrograms/100 ml after 1.5 to two hours and to 130.3 micrograms/100 ml in the course of 3.5 to four hours. An average level of 124.3 micrograms/100 ml had been reached after another 1.5 to two hours. The iron fixation capacities first declined and then went up again. The average iron level recorded from eight adult sows, weighing between 180 kg and 210 kg, was 75 micrograms/100 ml, when measured seven weeks from piglet weaning. The average iron fixation capacity was 488.3 micrograms/100 ml at the same time and for the same animals. The iron level did not change throughout testing. The average copper level was 230.9 micrograms/100 ml, at the beginning, but individual differences in behaviour occurred during the day. No difference was recorded, at the beginning, between gilts and adult sows for blood plasma protein, levels being 7.73 or 7.81 g/100 ml, and for haemoglobin in the blood, levels being 12.8 or 12.5 g/100 ml. Individual variations, however, with no clear-cut direction, occurred over the testing period.