1. The cytological and cytochemical properties of the Ehrlich tetraploid and hyperdiploid, TA3 tetraploid and diploid, Krebs 2B, sarcoma 37, MC1M, 6C3HED and DBA lymphoma, and lymphoma #1 ascites tumors at a fixed interval after transplantation are described. 2. No qualitative differences were observed in the cytochemical properties of the nucleus, nucleolus, parachromatin, parachromatin bodies, large lipide globules, lipochondria, mitochondria, and cytoplasm of the tumor cells of the 10 neoplasms. 3. Quantitative differences were noted in the cells of the 10 neoplasms. These were reflected by variation in nuclear and cytoplasmic diameter, nucleolar mode, mitotic index, incidence of gross abnormalities of mitosis, karyorrhexis, multinucleated cells, accessory micronuclei, cell clumping, and in the number and size of the large lipide globules and lipochondria of the cells.