Analytical methods used clinically in Sweden for detection and quantification of fetal hemoglobin (HbF) in maternal blood are either the microscopic method Kleinhauer Betkes test (KBT) or high performance liquid chromatography. A more modern alternative to detect and quantify HbF+ erythrocytes is flow cytometry. The aim of this project was therefore to evaluate the commercial kit "Fetal Cell Count kit" using flow cytometry. The kit used two antibodies; one directed against the specific γ-chain of HbF protein and the other directed against the intracellular enzyme carbanhydrase (CA), which is found in all erythrocytes in adults. The resulting data showed good precision, sensitivity and linearity. A reference interval based on male blood donors was determined to <0.1 % HbF+ erythrocytes and <1.3 %F-cells. The kit is well suited to detect and quantify F-cells. It could be used as a important tool to follow-up patients withβ-thalassemia and sickle cell anemia. However the kit was not as useful for detection and quantification of HbF+ erytrocytes in fetomaternal hemorrhage induced by Rhimmunization.