Mycobacteria are unusual causes of keratitis and other ocular infections but the outcome of infection is often serious. We report a case of keratitis due to Mycobacterium chelonae, a rapidly growing environmental mycobacterium, in a soft contact-lens wearer, and discuss the difficulty and delay in identifying the organism, twice erroneously identified as Nocardia asteroides on morphological grounds. Despite in vitro susceptibility, the response to anti-bacterial agents was negligible and a second keratoplasty was required after a recurrence of disease at the donor-host junction. We review the role of mycobacteria as the cause of keratitis and other forms of ocular disease.