Each study is different; we have studies that last as short as a day or may range up to a few years. The time it takes for you to participate is different for each type of study. At the beginning of a study, participants may need to be seen weekly. As the study progresses you will be seen less often, perhaps monthly or even just twice a year. Some studies require phone visits to review your health or to address any questions or concerns you may have during the course of the study.