Conclusions: Replacing chlorine atom in alpha position of carboxyl acid radicals by bromine atom do not affect specificity but reduce sensitivity about 8 - 10% in the specific esterase human leukocyte staining, naphthol AS-OL 2-bromopropionate is the highest activity and equivalence naphthol AS-D chloacetate of Sigma's product but the price is lower than ten times.