Cyclin E and p27Kip1 are co-regulators of the G1- to S-phase transition and closely related to tumor behavior. The purpose of this study was to examine expression of cyclin E and p27Kip1 in astrocytomas and to evaluate the relationships between expression of these cell-cycle regulators and prognosis of patients with astrocytoma. Tissue samples from 130 astrocytomas (WHO grade 1 n = 5, grade 2 n = 23, grade 3 n = 64, grade 4 n = 38) were examined immunohistochemically for cyclin E and p27Kip1 expression. Patient charts were reviewed for clinical presentation, and survival was followed. The cyclin E labeling index (LI) tended to increase with tumor grade (Kruskal-Wallis, P = 0.0104). For patients with primary astrocytomas, the 50% survival times for the low cyclin E LI (< 5%) group and the high cyclin E LI (> or = 5%) group were 53.7 months and 19.8 months. In combined analysis of cyclin E and p27Kip1 expression, the low cyclin E/high p27Kip1 LI (> or = 50%) group had the best survival (50% survival time: 103.2 months), the low cyclin E/low p27Kip1 LI (> or = 50%) and the high cyclin E/high p27Kip1 LI groups moderate survival (24.1 and 27.5 months), and the high cyclin E/low p27Kip1 LI group the worst survival (13.1 months). Multivariate analysis identified the combined factor, high cyclin E/low p27Kip1, as a novel independent prognostic factor for survival time (P = 0.0037, relative risk = 2.4). This study suggested that combined analysis of cyclin E and p27Kip1 expression was considered to be potentially useful in predicting the prognosis of patients with astrocytoma.