The potential psychological risks of falsely positive test results in neonatal screenings have not been studied previously. 20 000 newborns were screened for congenital hypothyroidism. Of the 144 positive tests, 137 were false. The families of 102 babies with false positives were explored in reference to their (1) initial parental psychic reactions (emotional reactions and abilities for coping) and (2) residual reactions 6 to 12 months later. 78 families initially exhibited strong emotional reactions. Providing information about a positive screening test is therefore an acute strain to the majority. After a period of 6 to 12 months there was in 18 families persistent insecurity regarding the baby's health. These concerns were linked to the family to the screening and the disease screened for. This may impair the parent-child relation and thus, the child's development. Thus a false positive test appear to trigger in the majority a development of a psychic crisis. 12 families seemed however to have been totally untouched by the potential threat of the information. The crisis is effectively solved by most (consideration must be paid to the integrated psychological support given to all). It is not known whether the 18 risk families actually have been iatrogenically hurt or if their worries brought to attention in connection with the screening merely represent habitual psychic maladjustment. Preparation for parenthood and education about screening principles are beneficial and important. This study demonstrates the importance not only of asking how much worry is elicited but also how this worry is being handled (coping ability) in order to provide a fair estimate as to which families are at risk.