Primary neoplasms of the pituitary gland are uncommon in children. Physiological enlargement of the gland, however, is universal and can sometimes be confused with a tumor. Due to widespread availability of MR imaging, the number of children referred to pediatric neurosurgeons with an enlarged pituitary associated with nonspecific symptoms, most commonly headache, is increasing. In this review, the authors illustrate two common causes of pituitary enlargement in children, namely physiological hypertrophy of puberty, more commonly seen in females, and secondary hyperplasia caused by hypothyroidism. The importance of early and accurate diagnosis, without recourse to extensive endocrine investigations or inappropriate surgery, is underscored.