p27^kip1 is a cyclin-dependent kinase inhibitor that regulates progression from G1 into S phase. Aberrations in cell cycle control are often observed in tumors d might even be necessary in tumor development. Recent reports showed that low p27^kip1 expression is associated with poor prognosis in several tumors and leukemia. To investigate the expression of p27^kip1 in malignant lymphomas and ucidate the role of p27^kip1 as a possible prognostic indicator, the authors performed an immunohistochemical staining of p27^kip1 correlated with Ki-67 labelling index and clinical parameters. p27^kip1 expression was reduced variably in most malignant lymphomas and inversely correlated with Ki-67 labelling index (p=0.0151). Regarding chemotherapeutic response, p27^kip1 expression in the complete remission group showed statistically significant difference in expression compared to the progressive disease group (p=0.0021). There were significant differences in survival between cases with low and high p27^kip1 expression (p=0.0071). In a multivariate Cox analysis, p27^kip1 expression was independent prognostic factors as well as other known prognostic factors including age, grade, stage and chemotherapeutic response. In conclusion, the study suggests that reduced expression of p27^kip1 protein may play a role in the pathogenesis and biologically aggressive behavior of malignant lymphomas.