This paper presents a case report of congenital hypothyroidism that illustrates some of the issues in screening for this disorder. Congenital hypothyroidism has several causes, the most common of which is thyroid dysgenesis. Most affected infants have no historical clues or physical findings to suggest diagnosis. Neonatal screening combining thyroxine and thyrotropin screening have resulted in increased detection, although false-negatives do occur, and the physician must carefully observe all newborns for the findings of congenital hypothyroidism. Early treatment improves the prognosis considerably. This paper reviews the pathophysiology, diagnosis, and treatment of congenital hypothyroidism.