Inappropriate expression of the Aurora kinases can induce aberrant mitosis, centrosome irregularities, and chromosomal instability, which lead to anueploidy and cell transformation. Here, we report that Aurora-A and Aurora-B are highly expressed in primary human and mouse prostate cancers and prostate cancer cell lines. In clinical samples, levels of Aurora-A and Aurora-B were significantly elevated in prostatic intraepithelial neoplasia lesions and prostate tumors when compared with the non-neoplastic samples. Interestingly, expression of Aurora-A in non-neoplastic prostates correlated with seminal vesicle invasion (ρ = 0.275, P = 0.0169) and in prostate tumor with positive surgical margins (ρ = 0.265, P = 0.0161). In addition, nuclear expression of Aurora-B in prostatic intraepithelial neoplasia lesions correlated with clinical staging of the tumor (ρ = −0.4, P = 0.0474) whereas cytoplasmic expression in tumors correlated with seminal vesicle invasion (ρ = 0.282, P = 0.0098). Cell lines and primary tumors derived from the TRAMP model were also found to express high levels of Aurora-A and Aurora-B. When human PC3, LNCaP, and mouse C1A cells were treated with the potent Aurora kinase inhibitor VX680, which attenuates phosphorylation of histone H3, cancer cell survival was reduced. VX680 could further reduce cell viability >2-fold when used in combination with the chemotherapy drug doxorubicin. Our findings support a functional relationship between Aurora kinase expression and prostate cancer and the application of small-molecule inhibitors in therapeutic modalities. (Cancer Res 2006; 66(10): 4996-5002)