Cyclin A is an S- and G2-M-phase regulatory protein, and its abnormal expression has been implicated in cellular transformation. This work was undertaken to investigate the frequency of cyclin A overexpression and the correlated clinical outcome in human hepatocellular carcinoma (HCC). Herein, 12 of 31 (39%) patients exhibited cyclin A overexpression in their tumorous tissues, resulting from gene amplification in 6 of 12 patients, (post)transcription in 4 of 12 patients, and (post)translation in 2 of 12 patients. Patients who overexpressed cyclin A had significantly more tumor cells in the S and G2-M phases compared with those expressing a normal cyclin A level (P = 0.007 and 0.039, respectively). Increased levels of Skp 2, a cyclin A-interacting protein, were also found in 17 of 31 (55%) of HCC patients who showed a trend to have more S-phase tumor cells (P = 0.07). By an unpaired Student's t test and a Fisher's exact or chi2 analysis, overexpression of cyclin A had a strong correlation with elevated Skp 2 expression and increased alpha-fetoprotein levels (P = 0.001 and 0.009, respectively), but it was not associated with patients' age, tumor size, cirrhosis, or the positive detection of hepatitis B virus surface antigen. In the disease-free survival analysis, patients whose tumors overexpressed cyclin A had a median disease-free survival of 6 months, whereas patients who lacked cyclin A overexpression exhibited a longer median period of 29 months (P = 0.046). The overall survival analysis revealed the same trend, i.e., cyclin A-overexpressing patients had shorter overall survival periods (median, 12 versus 50 months; P = 0.09). By multivariate analysis, the correlation of cyclin A overexpression with shorter disease-free periods remained significant after adjustment for Skp 2 overexpression and alpha-fetoprotein induction (P = 0.019). These data suggest that overexpression of cyclin A can be an independent prognostic factor for the tumor relapse of human HCC.