The objective of this work was to evaluate results of control epidemiological studies of iodine-deficiency condition in pregnant and breast-feeding women; the secondary objective was to develop standard prophylactic iodine dose schedule for these patients. The study included two groups of pregnant women treated either with a daily dose of 200 mcg potassium iodide (group 1, n=52) or with 300 mcg Kl/day (group 2, n=69). In all of them, blood TSH, free thyroxin and antithyroid peroxidase antibody levels were measured along with iodine excretion in urine. Thyroid volume was determined by ultrasound. Initially, median urinary iodine excretion in all the patients was 62.7 mcg/l. Three months after onset of the treatment with potassium iodide it significantly increased to 83.5 mcg/l and 1120.8 mcg/l in groups 1 and 2 respectively (p = 0.006 and 0.001). However, the desired level of >150 mcg/l was not achieved. Treatment with KI in the period of lactation within 2 months after delivery resulted in median urinary iodine excretion of = >100 mcg/l in 10.5% of the women in group 1. None of the patients in group 2 showed the required iodine concentration in the urine. It means that the minimal daily prophylactic dose of iodine for pregnant and lactating women should be 300 mg.