The development of relatively inexpensive radioimmunoassay techniques opens new possibilities for widespread screening for hypo- and hyperthyroidism in developing regions where iodine deficiency is great. From component cost analysis, it appears that radioimmunoassays of thyroid hormones can be performed in India for as little as 2.4 rupees (29 cents) per test. Cost-effectiveness analysis indicates that screening for hypothyroidism in iodine-deficient areas in India is, of alternative detection strategies, the most cost-effective: Cases are found at an average cost of 40 rupees ($4.80) per case. Cost breakdowns and considerations of convenience and acceptability indicate that filter paper methods may soon be preferred to whole-blood assays, especially for screening. Cost-effectiveness findings for these screening strategies and for reasonable modifications of them should be compared with the estimated cost-effectiveness of iodine supplementation in determining optimal health policy toward subclinical thyroid disease.