Fundamental evaluation of the subrenal capsule assay (SRCA) method in nonsolid tumors was made, using two types of murine malignant ascites. Malignant ascites were obtained from mice bearing M-5076 ovarian reticular cell sarcoma or MH-134 hepatoma. These tumor cells were allowed to settle by standing at 4 degrees C to form a jelly-like clot. This clot was cut into fragments about 1mm3 in size and one of these fragments was mashed in trypan blue to estimate the viability grade of the implanted tumor cells. The rest of the fragments were implanted beneath the renal capsule of the mice. On the 6th day after implantation, the assay mice were killed, the increase in the size of the tumor was determined and histological examination was carried out. The results were as follows: (1) The clot was formed reproductively by allowing ascites to settle for one or two days and there was a high viability rate for the tumor cells: 79.9 +/- 11.0% of M-5076 and 90.1 +/- 5.9% of MH-134. (2) The ascites clot thus implanted grew rapidly in the control groups but growth was inhibited by chemotherapy: Tumors were reduced significantly (p less than 0.05-0.005) in the group treated with a single agent. This trend towards a suppressive effect of carcinocidal agents on the tumor growth was more conspicuous as a combination regimen was utilized, a combination of three agents producing the maximum effect. (3) The clot grew more quickly than the solid tumor in both the control and the treated groups. There was a high correlation (r = 0.93 in M-5076, and r = 0.64 in MH-134) between the growth rates of ascites and solid tumor in SRCA. (4) Histological examination revealed that viable tumor cells infiltrated widely under the renal capsule in both types of tumors. These results suggest that ascites and solid tumor are useful materials for the subrenal capsule assay method.