This study was performed to specify the distribution and the heterogeneity of mast cells found in lungs and trachea of Van Cats. Four Van Cats were used in the study. Appropriate sized pieces were taken from the lungs and tracheas of the cats. After BLA (Basic Lead Acetate-Mota) was set, it was blocked with paraplast by doing the routine tissue follow-up. Sections taken in 6-7 mu m thickness were stained with 0,5 % toluidine blue and alcian-blue safranin O combined stain. Numbers of mast cells were specified semi-quantitatively in the sections stained with toluidine blue under lens 40. Among analysed organs, the most mast cells were found in lungs. To specify the granule construction, BLA detection was determined to be suitable. In the stain of Alcian-blue safranin O, SO (+), AB (+) granulose mast cells were found; mast cells that have mixed granules were not found.