The thyroid hormone deficiency on cardiovascular function can be characterized with decreased myocardial contractility and increased peripheral vascular resistance as well as with the changes in lipid metabolism. 42 patients with cardiovascular disease (mean age 65 +/- 13 yr, 16 males) were investigated if iodine insufficiency can play a role as a risk factor for the cardiovascular diseases. The patients were divided in 5 subgroups on the ground of the presence of hypertension, congestive heart failure, cardiomyopathy, coronary disfunction and arrhythmia. Urine iodine concentration (5.29 +/- 4.52 micrograms/dl) was detected with Sandell-Kolthoff colorimetric reaction. The most decreased urine iodine concentration was detected in the subgroups with arrhythmia and congestive heart failure (4.7 +/- 4.94 micrograms/dl and 4.9 +/- 4.81 micrograms/dl, respectively). An elevated TSH level was found by 3 patients (5.3 +/- 1.4 mlU/l). An elevation in lipid metabolism (cholesterol, triglyceride) associated with all subgroups without arrhythmia. In conclusion, the occurrence of iodine deficiency in cardiovascular disease is frequent. Iodine supplementation might prevent the worsing effect of iodine deficiency on cardiovascular disease.