Ten cases of Horner's syndrome with pharmacologic testing and computed tomography scans are described in patients up to age 8 years. The patients also were assessed for iris color and facial sweating. Classical preganglionic Horner's syndrome associated with brachial plexus birth injury was not identified in any case. Two patients who presented with ptosis had neuroblastoma. Two other children had undergone corrective cardiothoracic surgery. Two patients had major congenital abnormalities. In four patients, no cause of Horner's syndrome was determined.