Pervasive developmental disorder, not otherwise specified (PDD, NOS), a developmental-neurologic spectrum disorder, occurs in 10 to 12 of every 10,000 children. PDD, NOS is characterized by a spectrum of significant problems that may vary substantially in range and expression. These may include visual/spatial, kinesthetic, verbal/linguistic, and musical/ rhythmic problems. Social skill deficits are also common, as are restricted, repetitive patterns of behavior, interests, and activities. Symptoms of PDD, NOS are often expressed differently among children with the disorder and can be mistakenly attributed to other problems such as attention deficits, oppositional behavior, or stress reactions. Clinicians may encounter children in their practice who exhibit symptoms of PDD, NOS and must be familiar with this disorder so that appropriate diagnosis and treatment can be provided. Families also need on-going, anticipatory guidance to help them cope with the behavioral aspects of the disorder.