28 consecutive patients (age 15-58 years) with refractory acute leukaemia (24 AML, 4 ALL) have been treated with high or intermediate dose cytosine arabinoside (AraC). Twenty patients received AraC at a dose of 3000 mg/m2, twice daily for 6 days (13 patients AraC alone, 7 patients AraC and doxorubicin) and 8 patients received AraC at a dose of 1000 mg/m2, twice daily for 6 days and daunorubicin. 10 of the 20 patients treated with high dose AraC achieved a complete remission (50%) and 2 a partial remission. No patients in the intermediate dose AraC group achieved a remission (p = 0.05). Toxicity of these protocols was acceptable. Vomiting, headache, somnolence, fever, conjunctivitis, and minor cardiac arrhythmias were found most frequently. The pancytopenic period ranged from 16-30 days for the high dose protocol and 14-23 days for the intermediate dose protocol. Sophisticated isolation and blood banking facilities are required in this period. Median duration of remission was 6 months. Results obtained are in favour of the high dose protocol in refractory leukaemia. Only a large dosage increment of AraC can overcome refractoriness of leukaemic blast cells.