In January 1997 a new approach to preventing iodine deficiency was introduced in Poland. The goal of the present study was to determine whether the mandatory iodization of kitchen salt (30 mg KI/kg) has had any impact on ioduria.The study was performed on 29 healthy volunteers, aged 22-29 (average age 23.93 +/- 1.14), examined in 1996 and retested after 36 months of iodine supplementation in 1999. Each person underwent a physical examination and thyroid ultrasonography. The iodine level was determined using morning urine samples.For the duration of the study thyroid volume remained unchanged, ranging from 11.48 I3.89 ml in 1996 to 12.11 +/- 3.85 ml in 1998. The echostructure was normal in all subjects both in 1996 and in 1999. In 1996 the iodine concentration in urine (ICU) in the study group averaged 100.4 +/- 41.5 mg/L (range from 43.3 to 175.6 microg/L). Seventeen persons had an iodine concentration below 100 microg/L. In 1999 the average ICU was 140.7 +/- 78.87 microg/L. Three subjects had a lower ICU in 1999 (53.93 +/- 24.65 microg/L) than in 1996 (104.1 +/- 24.6 microg/L). These persons claimed to have completely eliminated the use of added salt in their diet.We conclude that mandatory iodine supplementation method is sufficiently effective when salt is used in the diet. In the case of restrictions on salt consumption the use of preparations containing iodine should be recommended.