A 6-month-old boy had a 2-week history of anisocoria. When examined, he had a small pupil on the left side but no ptosis. The mother reported that the pupil was sometimes normal in size. Initially, no tests were ordered. However, the child returned 1 week later because the mother had observed the occurrence of ptosis for the first time. The ptosis was on the same side as the miosis (Figure 1). The mother noted that there were times when there was no ptosis or pupillary involvement (Figure 2). At times during the office examination, only anisocoria without ptosis was observed. Occasionally, we saw anisocoria with a trace of ptosis of the upper eyelid, but careful scrutiny showed reverse ptosis of the lower eyelid (Figure 3). At other times, we observed significant ptosis without anisocoria (Figure 4). The mother was informed that this manifestation was rare and most likely physiological in nature. We recommended a computed tomographic (CT) scan of the neck and thorax to be certain there was no tumor. The mother was reluctant to approve a CT scan because of concerns about radiation exposure. Ultimately, she consented. The radiology department preferred a CT to a magnetic resonance image as calcium, which is sometimes seen in neuroblastoma, is easier to see with a CT. The CT revealed a neck mass, and 5 days later surgery was performed for a neuroblastoma of the paravertebral sympathetic chain. The tumor was completely removed and no chemotherapy was required. At the 6-month follow-up appointment, this patient had persistent left-sided Horner syndrome.