Aim: Gaucher disease is an autosomal recessive lysosomal storage disease caused by insufficient glucocerebrosidase activity resulting in accumulation of glucosylceramide, particularly in macrophages. Multiple myeloma and B cell lymphoma are considered to be one of the causes of death from GD in the long term. We aimed to compare cell surface antigens of leukocytes to try to identify a reliable marker for leukocyte infiltration and progression to lymphoid malignancy. Material ve Method: 10 Gaucher disease patients and 20 age-matched healthy controls were included. Leukocytes were collected from whole blood using a Ficoll gradient, stained for specific cell surface antigens (CD33, CD19, CD14, and CD8) and sorted by flow cytometry. Levels of each leukocyte cell surface antigen were expressed as a percentage of leukocytes expressing them. Leukocyte glucocerebrosidase activity was measured by fluorometry. Results: The percentage of CD19+ leukocytes in Gaucher disease patients (8.2 +/- 3.4) was significantly higher than in the control group (4.8 +/- 3.4) (p < 0.05). The percentage of leukocytes expressing CD33 (12.8 +/- 6.6 vs 7.9 +/- 8.0, p=0.077), CD14 (10.6 +/- 4.6 vs 7.1 +/- 6.9, p=0.094) or CD8 (12.7 +/- 5.3 vs 9.8 +/- 5.9, p=0.115) was not significantly higher in patients than in controls. Discussion: The higher levels of CD19+ leukocytes may serve as a useful marker to predict leukocyte infiltration and perhaps also malignancy in Gaucher disease patients. Experimental anti-CD19 drugs are in development for the treatment of B cell cancers, and CD19+ leukocyte levels may also serve as a marker of the response to this treatment.