The aim of the study was to compare iodine utilization from different sources by sows and their progeny and the levels of T(3) and T(4) in their serum.Pregnant Czech Large White x Landrace sows were fed with an experimental KPK diet (a diet for lactating sows) 14 days before parturition until weaning (at a piglet age of 28 days). In group A (n=50, 10 sows, 40 piglets) the feed was supplemented with KI (0.6 mg of iodine per kg of feed). Iodine enriched alga Chlorella spp. (0.6 mg of iodine per kg of feed) was used as a supplement in group B (n=50, 10 sows, 40 piglets). In group C (n=50, 10 sows, 40 piglets) the sows were injected i.m. with IFAE at a dose of 100 mg of iodine per sow. Iodine, T(3) and T(4) were measured in each group for comparison of iodine utilization.Our results indicate a good utilization of iodized oil by sows. However, its transfer into milk is lower compared to the other iodine sources.