['To investigate the clinical role of Aurora kinases (essential for regulating mitosis) in human bladder pathogenesis, by quantifying Aurora kinase A and B, phospho-Aurora A, and phospho-Rb and p53 in bladder tumours, analysing the correlations between expression and clinicopathological features.', 'We evaluated levels of Aurora A, B, phospho-Aurora A, phospho-Rb and p53 in 73 superficial bladder tumours using tissue microarrays and immunohistochemistry, and correlated expression with pathological variables and clinical outcome.', 'None of the Aurora proteins, when analysed alone, significantly predicted either tumour recurrence or progression. In tumours with an aberrant G1 checkpoint, assessed by phospho-Rb and p53 status, expression of neither Aurora A nor its phosphorylated form predicted either tumour recurrence or progression. Surprisingly, high expression of Aurora B in tumours with an aberrant G1 checkpoint significantly protected from tumour recurrence. On multivariate analysis, Aurora B was the only significant factor that predicted tumour recurrence in the presence of either phospho-Rb or mutated p53. This difference was not evident in tumours with an intact G1 checkpoint.'] Is aurora kinase B an independent protective factor in superficial bladder tumours with a dysfunctional G1 checkpoint?