To get a high recovery rate of mast cells from the rat peritoneal cavity, a new modified method was discussed using BSA density gradient. Three procedures, peritoneal lavage, washing of peritoneal cells and purification by BSA, were tested in this study, and the numbers of total cells and mast cells in each procedure were calculated. The recovery rate was the highest in BSA density gradient purification of the cells washed once with low speed centrifugation. The recovery rate was 73.7% and the number of mast cells taken from one rat was approximately 1.5×10(6). The purity of the cells with this procedure was 95.0% (range from 93.0 to 96.0%).