We assessed Stanniocalcin-1 (STC-1) mRNA expression in human normal tissues, various types of human cancer cell lines, and cancer tissues obtained during surgery. Using a reverse transcriptase-polymerase chain reaction (RT-PCR) assay developed to detect STC-1 mRNA, the transcripts were detected in 20 out of 21 cancer cell lines and in all tumor tissues from various types of cancer. Semi-quantitative analyses with multiplex RT-PCR showed that STC-1 mRNA tended to be enhanced in cancer tissues of hepatocellular carcinoma and colorectal cancer compared to background cancer-free tissues. Analysis of blood samples obtained from 11 patients with hepatocellular carcinoma before, after and during hepatectomy showed STC-1 mRNA expression in 8 out of 11 patients at least one time. Normal donor blood samples (n=31) were all-negative for STC-1 mRNA expression. Our results indicate that STC-1 mRNA might be a useful molecular marker for detection of tumor cells in blood from patients with various types of malignancies.