We treated two sporadic cases of postoperative endophthalmitis caused by rapidly growing (Runyon's group IV) mycobacteria. Both involved intraocular lenses, one a secondary implant after intracapsular cataract extraction (Mycobacterium chelonae subspecies abscessus) and the other a primary posterior chamber lens implantation after extracapsular cataract extraction (pigment-producing member group IV). Signs of inflammation were judged severe enough to warrant diagnostic and therapeutic intervention during the fourth postoperative week in both cases. In both eyes the organism seemed to be eradicated by intravitreal amikacin in combination with vitrectomy, as well as topical, subconjunctival, and, in one case, systemic antibiotic therapy.