AIM: To validate a radioactivity assay, the TCA-RA method,for the measurement of C-1027 in serum and to evaluate its application in determination of pharmacokinetics of C-1027 in mice.METHODS: 125I-C-1027 was prepared by the Iodogen method and separated by HPLC. The radioactivity assay was established and used to determine 125I-C-1027 in mice at doses of 10, 50 and 100 μg/kg after precipitation with20% trichloroacetic acid (TCA-RA method). Severalpharmacokinetic parameters were determined after intravenous injection of 125I-C-1027 to mice.RESULTS: After intravenous injection of 125I-C-1027 to mice,at doses of 10, 50 and 100 μg/kg; the apparent distribution volumes (Vd) were 0.26, 0.31 and 0.33 L/kg; the biological half-lives (T1/2) were 3.10, 3.40 and 3.90 h; the areas under curve (AUC) were 18.41, 103.69 and 202.74 ng/h/mL; the elimination rate constants (K) were 1.04, 1.26 and 0.58/h;and the total body clearance (Cl) were 0.54, 0.48 and0.49 L/kg/h, respectively.CONCLUSION: TCA-RA is a sensitive, reliable and suitable method for the determination of 125I-C-1027 in mouse serum.