Psoriasis is a common chronic immune mediated disease. There is increasing evidence demonstrating that psoriasis patients have an increased risk of lymphoproliferative malignancies. The evolving therapies for psoriasis target the immune system and therefore, these treatments may further increase the rate of lymphoma in psoriasis patients. To study lymphoma outcomes in psoriasis patients a large cohort of patients needs to be followed for many years. This proposal will rigorously investigate the validity of the General Practice Research Database (GPRD), a medical record database in the United Kingdom with 9 million patients and over 35 million person years of follow up, for performing high quality population based epidemiology studies in psoriasis patients. This aim will help develop an extremely useful tool for conducting population based studies in psoriasis patients. We will then perform a large cohort study in the GPRD population to determine if psoriasis is associated with an increased risk of lymphoma. This aim will have important implications for monitoring the safety of immunosuppressive therapies in psoriasis patients. Finally, we will develop additional methodologies for assessing the extent of psoriasis skin involvement to determine the impact this variable has on lymphoma and other outcomes for use in studies of psoriasis in the population at large. This aim will provide a rigorously validated method for classifying severity of psoriasis for use in a variety of future psoriasis studies. A second major goal of this application is to provide the mentoring and additional training necessary for the candidate to become an independent investigator. The candidate has established mentoring relationships with leading senior investigators that will be fostered through the studies planned in this application. The candidate will also pursue additional formal training in advanced level graduate courses in epidemiology in order to allow him build upon the foundation of expertise he has built through his previous training in epidemiology at the masters level. Through the combination of the research program, mentoring program, and additional coursework outlined in this application the candidate will be well prepared to be an independent investigator concentrating on improving the lives of patients suffering with dermatologic disease.