The M@CBETH (MicroArray Classification BEnchmarking Tool on Host server) web service, available at http://www.esat.kuleuven.be/MACBETH/, offers a simple tool for making optimal two-class predictions in a clinical setting [3]. This web service compares different classifiers and selects the best in terms of randomized test set performances. The M@CBETH website offers two services: benchmarking and prediction. Benchmarking involves selection and training of an optimal model based on a benchmarking dataset. This model is stored for immediate or later use on prospective data. The prediction service offers a way for later evaluation of prospective data by reusing an existing optimal prediction model, which is useful for classifying new unseen patients. Nine different classification methods are considered. Application of the M@CBETH benchmarking service on two binary classification problems in ovarian cancer confirms that it is important to select and train an optimal model for each microarray dataset.