Neuroblastoma almost always arises in association with sympathetic neural crest tissues that flank the spinal axis, including the paravertebral sympathetic ganglia of the neck, mediastinum, retroperitoneum, and pelvis, or in the adrenal glands. Neuroblastoma in the newborn period, which can present as localized or metastatic disease, often resolves spontaneously and requires little or no therapy. The authors describe a 5-week-old infant with an isolated primary neuroblastoma arising in the deltoid muscle. Histologic and biologic characteristics were consistent with a favorable-prognosis stage 1 neuroblastoma. Following a complete local excision, the child remains in complete remission 3 years from diagnosis.