Among 1879 children with the diagnosis of acute lymphoblastic leukaemia made up to Dec 31 1987 in 863 cases (45.92%) treatment was discontinued. They were followed up till Dec 31 1989. The median follow-up was 3 years and 14 months. In 811 cases the treatment was discontinued during the first complete remission, in 56 cases after a relapse during initial treatment. In the time period when the programmes St. Jude and LSA2L2 were used the per cent of children with treatment withdrawal was 38.22%, but it rose to 53.01% when a more intensive programme BMF had been introduced. The probability of 7-year disease free survival after treatment discontinuation was 69.5% and 76.2% respectively. In 186 cases (21.6%) relapses developed., mostly in the first year after treatment discontinuation, but even after 7 years the risk of relapse was 2.46%. Ninety-six children (11.2%) died, 761 (88.8%) are alive, among them 671 in the first complete remission. Apart from therapy intensity, a statistically significant beneficial effect on disease free survival had discontinuation of treatment during the first complete remission, and sex--the prognosis was better in girls. In three cases secondary neoplasms were found.