Five children with previously undiagnosed retinoblastoma had signs of unilateral orbital cellulitis and were treated with systemic antibiotics, corticosteroids, or both. When retinoblastoma was finally diagnosed clinically, radiologists believed in every case that, on the basis of the soft-tissue swelling seen with computed tomography, there was orbital extension of the tumor. However, intraoperative and histopathologic observations disclosed no demonstrable orbital tumor involvement. The affected eyes all had neovascular glaucoma, and all harbored highly necrotic tumors that were contained within the eye. We concluded that orbital inflammation can occur with retinoblastoma confined to the eye and that signs of orbital cellulitis do not necessarily imply orbital extension of the tumor.