Fresh lyraphoreticular tissues obtained from 14 cases of chronic hyperplastic tonsillitis and 4 cases of reactive hyperplasia of tonsils were studied for the enzymic activity of the acid ?-Naphthyl acetate esterase(ANAE). Imprints of the fresh lymphoreticular tissues were made. Then they were fixed according to the Mueller's method. Cryostal frozen section and paraffin section with ANAE stain were made. A part of the fresh lymphoreticular tissues was fixed with 10% formalin solution. Finally, cryostal frozen section and paraffin section with ANAE stain were made of the formalin-fixed tissues on the 10th, 20th and 30th day of fixation respectively.The rates of the cells positive for dot-like positions of different preparations were compared. It was found that the positive rate was the highest in the fresh frozen sections, then in the fresh imprints and fresh paraffin sections. The longer the tissues were preserved with formalin, the lower the rate of the posititive cells. The positive rate was nearly zero in the tissues after 30 days of formalin fixation.