A 46-year-old woman with a history of breast carcinoma and no known metastatic disease presented with iridocyclitis and secondary glaucoma. Intraocular inflammation and pressure elevation persisted despite standard medical therapy, and paracentesis was performed. Cytological examination of the aspirate revealed adenocarcinoma. Subsequent studies disclosed no evidence of extraocular metastasis. Two courses of radiation therapy to the involved eye resulted in a dramatic reduction in intraocular inflammation and allowed temporary control of the intraocular pressure. Ultimately, however, progressive glaucoma necessitated enucleation. This case confirms previous statements that iridocyclitis may be the initial clinical manifestation of metastatic malignancy. In addition, this report emphasises the importance of paracentesis in the diagnostic evaluation of selected cases of anterior uveitis of unknown aetiology.