Case report of a 4-year-old girl in whom a unilateral ocular localization appeared after 1 1/2 year of maintained remission of acute lymphoblastic leukaemia. The evolution of this localization can be divided in three phases: 1. During the first 17 months, an apparent simple relapsing conjunctivitis of the left eye. 2. During the following 5 months, repeated episodes of the left iritis with mydriasis and discolouration of the iris. 3. Finally, left uveitis involving the anterior chamber, with hypopion, hyphaema and glaucoma; the clinical presentation at this stage was suggestive of ocular lymphoblastosis. Radiotherapy to the lesion (total dose, 1 200 rads) was quickly followed by resolution without sequelae. No relapse was observed during the following 30 months, till death. The ocular disease remained the only manifestation of leukaemia during its evolution. A haematological relapse occurred 11 months after cure of the iritis, followed 1 year later by a second, treatment-sensitive relapse, and finally by a third, fatal relapse. The patient survived 5 years 9 months.