Twenty-four children with Williams syndrome underwent systematic neurologic evaluations. Abnormalities of mental status, motor coordination, tone, and gait were most prevalent. Tone abnormalities varied as a function of age, with younger children frequently exhibiting decreased tone and older subjects almost exclusively having increased tone. The gait and coordination abnormalities persisted among older subjects, indicating that they were not simply maturational problems. Physicians caring for such youngsters need to be aware that a variety of neurologic abnormalities are common in Williams syndrome and may change or progress over time. Neurologic examinations that reveal findings beyond the typical pattern that we report may raise suspicion for added neurologic insult and warrant further investigation.