From 1981 to 1986, in children with ALL and initial WBC > or = 50,000/mm3, over 6-year disease-free survival was significantly lower (33%) than in children with WBC < 50,000/mm3 (60%). In attempt to improve this unsatisfactory results, three modified American protocols named: "New York", "New York I", and "New York II", "New York I", and "New York II" were introduced consecutively in the centers of Polish Pediatric Leukemia Lymphoma Study Group (respectively, in 1987, 1997, and 1999). The treatment results achieved in three consecutive therapeutic groups of children with ALL and initial WBC > or = 50,000/mm3: group I--213 children (1987-1996), group II--58 children (1997-1999), and group III--52 children (1999-2001) are presented. The observation was completed in December 31, 2002. In three evaluated groups the first complete remissions (CRs) were achieved in 90.6%. 94.8%. and 94.2% of patients, respectively. Relapses occurred in 71 patients of group I (37%), in 9 patients of group II (16%), and in 6 patients of group III (12%). The complications of treatment caused death in 7 children of group I, in 1 child of group II, and in 2 children of group III. Eighty-one (38%), 11 (18.9%), and 9 (17.3%) patients, respectively, died due to progression of disease. The event-free survival (EFS) in three evaluated groups did not depend on age of children and WBC. The rates of 2-, 5-, and 10-year event-free survival (EFS) in group I were: 69.9%, 55.3%, and 53.6%, respectively and the rates of 2- and 5-year EFS in group II were: 80.7% and 72.7%, respectively. The rate of 2-year EFS in group III was 71.6%. The analysis of achieved treatment results in three evaluated groups shows the gradual improvement of the prognosis in children with ALL and initial WBC > or = 50,000/mm3 treated with the use of modified protocols "New York" and "New York I" in comparison with patients treated before 1987. Longer observation is needed for evaluation of efficacy and complications of "New York II" protocol.