The aim of this study was to investigate the incidence of congenital hypothyroidism (CH) in the West Black Sea Area, a mild-to-moderate iodine deficient area in Turkey. Neonatal screening for CH was performed using blood specimens collected onto filter paper. Thyrotropin [thyroid-stimulating hormone (TSH)] was measured by radioimmunoassay, and a value >20 mu U/ml was considered as cut-off point for re-examining. Venous serum was obtained to measure TSH, thyroxin (T4), free T4 (FT4) and thyroglobulin (TG). To determine the iodine status of the study area, median urinary iodine was measured in 212 randomly selected neonates and their mothers. A total of 18606 neonates were screened from three cities (Bolu, Duzce, and Zonguldak) between 2000 and 2002. With a cut-off point of TSH value >20 mu U/ml, the recall rate was found 1.6%. Eight cases of CH were diagnosed (incidence 1/2,326).There were three cases of transient hypothyroldism, with an incidence of 1/6202. Twenty-six percent of the TSH values was greater than 5 mu U/ml. Median urinary iodine concentrations in neonates and their mothers were 85 mu g/l and 40 mu g/l, respectively. The incidences of CH, transient hypochyroidism and the recall rate were higher in our study area than many countries in Europe. The study area has been affected by mild-to-moderate iodine deficiency. Neonatal screening for CH should be introduced in Turkey without delay. A national comprehensive infantile hypothyroidism and iodine prophylaxis policies should be developed.