This paper presents a real-world application for assisting medical diagnosis and drug prescription, which relies on the exclusive use of machine learning techniques. We have automatically processed an extensive biomedical literature to train a categorization algorithm in order to provide it with the capability of matching symptoms to MeSH descriptors. To interact with the classifier, we have developed a multilingual web interface so that professionals in medicine can easily get some help in their decisions about diagnoses (lookfordiagnosis.com) and prescriptions (lookfortherapy.com). We also demonstrate the effectiveness of this approach with a test set containing several hundreds of real clinical histories.