The use of ultrasound in evaluating neurologic diseases of childhood. Real-time cranial sonography, intracranial Doppler, and neuromuscular sonography are the sonographic techniques that are applicable to the neurologic evaluation of infants and children. Although limited by age, specificity, and operator skill and experience, the advantages of real-time cranial and intracranial Doppler sonography make them useful techniques in the evaluation of the young infant, particularly in the serial assessment of ventricular size and in the study of the critically ill infant. The use of neuromuscular sonography in the assessment of the floppy infant and in the guidance of biopsy makes this an increasingly valuable tool. 