[en] A sensitive, semi-quantitative radioimmunoassay method to screen for elevations of TSH concentration in blood is described. The method requires two 0.32 cm dots of dried blood-impregnated filter paper (equivalent to 3 μl plasma) and a 3-day incubation. Separation of bound and free is obtained using polyethylene glycol. The method can recognize TSH concentrations as low as 22 μU/ml using a highly sensitive antiserum developed by one of us (AFP). TSH in dried cord and newborn blood from four infants with congenital hypothyroidism was clearly higher than in normal infants. The method is suitable for use in a newborn screening program to confirm the suspicion of primary hypothyroidism in specimens with low T₄ concentrations