Mesothelioma is an aggressive cancer that affects the outside lining of the lung (the pleura). It is caused by previous asbestos exposure, often more than 40 years previously. Mesothelioma diagnoses have increased steadily over the past decade, in the UK and worldwide, and are predicted to continue rising over the next decade. The average life-expectancy of a person diagnosed with mesothelioma is less than a year. This is because it is very difficult to treat, with only one effective chemotherapy. On average, this chemotherapy allows people to live 3 months longer, although some people respond really well and go on to live for many months or even years. Unfortunately at the moment, we can’t predict which people will respond well to chemotherapy. Lots of new treatments are being developed for mesothelioma, and many hospitals, including ours, are running clinical trials testing these treatments in willing patients. We want to learn more about mesothelioma, specifically whether there are any patient characteristics, tumour factors or blood tests that will allow us to predict which patients might live longer or respond well to chemotherapy. Finding this out will allow us to give patients more specific information about what they can expect of their disease, and will help us make better treatment decisions for individual patients. To do this, we plan to collect clinical information and samples of blood and pleural fluid on patients diagnosed with mesothelioma at a number of hospitals in the UK. We will collect this information at the point of diagnosis and at routine clinic appointments attended by patients. We will also use the information to identify patients who are suitable to participate in clinical trials. If they agree, then their data will be used to assess their suitability for clinical trials, as and when they become available.