In this study, serum samples from 50 patients with the diagnosis of Behcet’s disease and 20 healthy volunteers were analyzed. The study consists of three parts. In the first part, paraoxonase (PON) activities were determined in the serum samples of 50 patients with Behcet’s disease and 20 healthy people. In the second part, equal volumes of serum samples from 50 patients were pooled and PON enzymes were purified by using Sepharose-4B-L-tyrosine tyrosine-1-naphtylamine affinity column. Optimum temperature, optimum pH, Vmax and Km values of the pure enzymes were determined. The same purification procedure was also performed in the serum samples of 20 healthy people. Electrophoretic mobility was observed (via SDS-PAGE) in the PON enzymes that were purified from the serum samples of patients with Behcet’s disease and healthy people. In the third part, in vitro effects of drugs containing azathioprine, methylprednisolone and colchicine that have already been used for the treatment of Behcet’s disease were tested on the PON enzymes of the patients with Behcet’s disease and control group. IC50 values and Ki constant values were measured and inhibition types were determined for the drugs containing azathioprine, methylprednisolone and colchicine that have already been used for the treatment of the Behcet’s disease and demonstrate in vitro inhibition effects.