Leukocyte Alkaline Phosphatase (LAP) or Neutrophil Alkaline Phosphatase (NAP) activity is demonstrated by an Azo dye coupling technique. Leukocyte alkaline phosphatase is determined in blood or bone marrow films. A scoring system has been developed based on the LAP activity presenting in the form of intensity of staining of Neutrophils. The stained neutrophils are scored as 0, +1, +2, +3, and +4. After counting a total of 100 neutrophils the total score gives the final result. Normal blood smear may have a score of 15–110. The LAP score is high in cases of Leukemoid reactions and low in Chronic Myeloid Leukemia (CML). The procedure described here is based on Sigma methodology.