Paraproteinemic crystalline keratopathy is an uncommon complication of multiple myeloma and other plasma cell dyscrasias. A case of 16 years' duration was associated with an IgG kappa monoclonal gammopathy and recurrent uveitis. The corneal changes were unusually extensive and distributed throughout all corneal layers. The deposits consisted of diffuse, small, polymorphic aggregates, which were iridescent in the superficial cornea, mat elsewhere, and associated with a diffuse stromal haze; specular microscopy showed additional features. Both corneas were thickened. The deposits failed to stain histochemically, except patchily with Masson Trichrome. There was extensive immunohistochemical labeling for IgG, kappa, and surprisingly, lambda. Ultrastructurally, pleomorphic deposits were found in every corneal cell; paracrystalline deposits with internal banding were seen only in the basal epithelium. Keratocytes and endothelial cells were damaged and reduced in number. Disease recurred in a corneal graft. Three main types of paraproteinemic keratopathy can be distinguished. The deposits probably represent various metabolic products of the monoclonal protein. This is not necessarily a benign condition; hematologic control may be necessary on purely ophthalmological criteria.