Hepatocellular carcinoma (HCC) is now the first leading cause of male and the second of female cancer mortality in Taiwan. In a preliminary microarray data-mining, we identified that STMN1 was up-regulated in HCCs. This study was aimed to establish the STMN1 expression profiles in assorted cancer cell lines and HCC tissues. The STMN1 genomic DNA is 1.5 Kbp in length, mapped to the 1p36.1-p35 and encodes for an 18 KDa polypeptide in the human. STMN1 is a ubiquitous phosphoprotein that promotes microtubule catastrophe and spindle assembly during cell cycle. In addition, STMN1 protein is also a cofactor to regulate the angiogenesis, cell migration and invasion. The role of STMN1 in the onset or progression of HCC is still not clear. In this study, we firstly examined the STMN1 mRNAs expression profiles in several cancer cell lines and found its significant up-regulation in six HCC cell lines, HA22T, HCC36, Hep3B, Huh7, Malaru, SK-hep1, one breast tumor, BCM1 and one stomach tumor, SCM1. To further understand if any amplifications of genomic STMN1, the expression profile of STMN1 mRNA and STMN1 protein in HCC tissue specimens, 62 HCC tissues, in pair, that collected from Chi-Mei Medical Center (Tainan) were analyzed. Among 62 pairs of HCC tissues analyzed, 47 STMN1 mRNAs were significant higher in HCC tissues than in their normal counterparts. On the other hand, the STMN1 genomic DNA was amplification in 27 HCC tissues. Then, we have determined and compared the STMN1 protein in both HCC tissues and normal tissues by the Western blotting analysis. STMN1 protein expression was found to be higher in 30 tumor tissues than in their corresponding normal tissues. This result was 84% consistent with the quantitative RT-PCR results. Furthermore, STMN1 CDs were cloned from HCC cell line (Sk-hep1) and subcloned into various protein expression vectors for further examining STMN1 subcellular localization in HeLa and Sk-hep1 cell lines. The STMN1 protein locates in both cytoplasm and nucleus by immunofluorescence analysis. This result was different from the previously report that STMN1 located in cytoplasm. Furthermore, there were 7% of Sk-hep1 cells which STMN1 proteins were only located in nucleus.