The paper in devoted to a rare condition difficult to diagnose, intraocular lymphoma. Five patients with a disease history of 2 to 6 years were examined. The authors describe clinical features of the condition and histologic and electron microscopic findings. The clinical pattern of malignant intraocular lymphoma in polymorphous, therefore virtually every case with a sluggish uveitis or posterior scleritis resistant to common therapy has to be verified. A hematologist should take part in examination of such patients. Since the involvement is local, as our findings evidence, a course of polychemotherapy is necessary for such patients.