The positivity for four cytochemical reactions, acid phosphatase (AcP), alpha-naphtyl acid acetate esterase (ANAE), beta-glucuronidase (BG), and N-acetyl beta-glucosaminidase (NABG) was correlated to first remission duration in 120 children affected with non-T, non-B acute lymphoblastic leukemia (ALL). The percentages of patients remaining in complete remission at 72 months were always higher for children whose blasts lacked these enzymatic reactions; however, a statistical difference was found only between BG+ and BG- ALL. It also appears that more complete enzymatic patterns of leukemic cells are associated with a poorer prognosis. The percentage of patients still in their first remission was 89% for leukemias with no cytochemical markers, 59% when one reaction was present, but less than 39% when two or more enzymes were detected in the blasts. It is noteworthy that the blasts of patients with more severe prognosis demonstrated a simultaneous positivity for AcP-ANAE or BG-NABG cytochemical reactions. The possible usefulness of these cytochemical markers to detect subsets of patients with different prognostic significance among non-T, non-B ALL is discussed.