Recognition of needle-like crystals in the cornea of a patient with deteriorating visual acuity initiated laboratory studies which demonstrated underlying multiple myeloma. Crystal deposition in the cornea occurs only rarely in multiple myeloma, and evidently reflects an unusual tendency for certain paraproteins to form numerous small aggregates which are deposited particularly within, and between, corneal epithelial cells. Treatment with chemotherapy, plus repeated plasma exchange with a normal plasma protein product resulted in significant depletion of crystals, and improvement in visual acuity over a period of three weeks. Accelerated clearance of paraprotein by plasmapheresis appeared to contribute materially to the rapidity of recovery, since recovery was considerably faster than in reported cases where treatment was with chemotherapy alone.