Thirty-one patients with newly diagnosed acute lymphoblastic leukemia were examined before receiving any treatment and their clinical and laboratory data were analyzed in order to determine the possible correlation between clinical presentation, morphologic sub-classes, cytochemical reactions, immunological phenotypes and cytogenetic findings. Each of the previous parameters and response to therapy were also examined for correlation. The analysis of clinical and laboratory characteristics of patients according to their immunological phenotype did not show any significant male sex bias, age distribution, hepatomegaly or splenomegaly at diagnosis. The analysis of clinical response of patients did not demonstrate any significant influence of sex, age, initial WBC count or the presence of a big tumor mass at diagnosis. There were no significant differences between our two major immunological subclasses Non-T CALLA+ ALL, and Pre-T ALL regarding proportions of patients in continuous remission, and relapse-free survival durations. The analysis of clinical and laboratory characteristics of patients on the basis of their chromosome categories did not show any significant sex bias, age distribution, initial WBC count, tumoral presentation or morphological subtypes at diagnosis, although there was an apparent male predominance in the pseudodiploid category and female predominance in the hyperdiploid category. Our results concerning the prognostic implication of CALLA were contradictory to those of several other investigators.