Background: CD34 a 110- to 115-Kda transmembrane sialoglyco pro- V twin, is expressed by early hematopoietic (myeloid and lymphoid) progenitor cells, endothelial cells, murine embryonic fibroblasts, and bone marrow (BM) stromal cells and their precursors. CD34 expression has great importance in diagnosis, classification and management of acute leukemia. Aim of the study: To evaluate the expression of CD34 (percentage and meanfluorescence intensity) in Sudanese patient with acuteleukemia. Materials and Methods: This is descriptive cross-sectional study, conducted in Flowcytometry centre in Khartoum state, 50 new cases of acute leukemia analyzed by flowcytometry for CD34expression. The flowcytometery lysing procedure for bone marrow aspiration and peripheral blood monoclonal antibody combination was done as the follows: All tubes were labeled then pipette into each tube 20 µL of CD34 monoclonal antibody and added 100 µL of sample containing no more than 1 x 104 leukocytes / ml. The tubes were vortex for 5 seconds, then incubated at room temperature (18-25 °C) for 10 minutes, then added 1 ml of the "fix-and-lyse" mixture to the tube and vortex immediately for two seconds, after incubated at room temperature for at least 10 minutes, all tubes were run on flowcytometer. Statistical analysis was performed using statistical package for social science (SPSS) software (version 16 for windows 7). Evaluations of patients' data were performed using the Chi-square and One way Anova. Results with p.value < 0.05 were considered statistically significant. Result and discussion: In this study we found that most case of AML were positive for CD34 while some cases of ALL were positive. All cases of biphenotypic and undifferentiated were positive so we found that (P.value = 0.012) of CD34 remark was significant between the groups of acute leukemia, also we found (69%) of B cases was positive and all cases of T cell was negative with significant (P.value = 0.013), so we can use the positivity of CD34 in exclusion of Tcases. This result was agree with Ching-Hon Pui (9) which found (70%) of B case were positive, also CD34 was reported by Mansoura(10) study to have the highest positivity in AML-M0 followed by AML-M1/M2 subtypes, this result were agreement with our study (CD34 positive in M0, M1, M2) therefore, we can use the negativity of CD34 in exclusion of these three type. Conclusion: CD34was positive in most cases of leukemia and have important role in differentiation between acute leukemia.