Neonatal screening for congenital hypothyroidism using T<sub>4</sub> and TSH measurements from blood-spotted filter paper is a well-established method. However, it has not been used to monitor T<sub>4</sub> and TSH concentrations in the follow-up of these children. In 22 treated children with congenital hypothyroidism whom we follow up in our Clinic, T<sub>4</sub> and TSH concentrations were concomitantly measured from venous blood and blood-spotted filter paper. There was a significant positive correlation between both T<sub>4</sub> and TSH measurements from venous blood versus blood-spotted filter paper (r = 0.7, p = 0.001; r = 0.78, p < 0.05). Filter paper T<sub>4</sub> values above 7 µg/dl could exclude hypothyroxinemia in 98% of the specimens. When TSH values were above 10 µU/ml, it was confirmed in 94% of the specimens, and when they were above 20 µU/ml, it was confirmed in 97% of the specimens. Measurements of both filter paper T<sub>4</sub> and filter paper TSH did not increase the reliability of the results obtained by examining the two hormones separately. We therefore suggest that filter paper T<sub>4</sub> and/or TSH measurements have distinct advantages in monitoring the treatment of children with congenital hypothyroidism. It can be performed in the community, enabling assistance in the follow-up of children in remote areas who are unable to show up for serum tests. The results are obtained quickly and allow improved follow-up by providing useful information such as excluding hypothyroxenemia or suggesting the possibility of noncompliance, and by a psychological effect on parents. However, they cannot replace serum T<sub>4</sub> and TSH measurements altogether.