The biochemical effects of CHIP have been studied in C3H mice with and without transplanted mammary tumour. The maximum tolerated dose of CHIP was first determined by lethality and intestinal crypt assays to be 40 mg kg-1 and this dose was used to assay the time course of gastric distension and the pattern of drug distribution. A high level of CHIP uptake was found in liver as well as kidney. For this reason, tests for both kidney and liver damage were undertaken up to 60 days post-treatment using a dose of 10 mg kg-1 Neoplatin for comparison. Despite the high level of platinum drug uptake in liver, there was no biochemical evidence of hepatocellular or cholestatic damage. From the renal point of view, there was the expected rise in serum urea after Neoplatin but not after CHIP and there was also a rise in urinary NAG after Neoplatin in tumour bearing mice. There was, however, evidence of suppression of protein levels including enzymes, following treatment with both drugs. Tumour-bearing mice respond differently from normal mice following treatment with platinum drugs. The study confirms that CHIP is less toxic than Neoplatin.