We evaluated the distribution of TSH levels on dried blood spots (Delfia system-threshold value for recall 20 microU/ml) in 27,282 consecutive samples examined during 1993, in the Emilia-Romagna region. We also evaluated, by questionnaire, the frequency of iodine disinfection in the perinatal period in all centers that do blood spots. We also evaluated the distribution of TSH spot values according to the localization of the center in endemic or not endemic area of the region. Among the parameters we considered, only the sampling day (p < 0.02) and the maternity center (p < 0.0001) showed a significant influence on TSH spot values. With regard to the questionnaire, the centers which habitually used iodine disinfection in obstetrics (20/28) showed significantly higher percentages of TSH values over 10 microU/ml than the centers which did not use (3/28) or rarely used (4/28) this type of disinfection (p < 0.0001). The only center which used regular iodine disinfection of umbilical cord in all newborns, showed a percentage of TSH values over 10 microU/ml (25.8%) and a recall rate (2.5%) significantly higher than all other centers (p < 0.0001).