Mycosis fungoides is one type of T cell lymphoma characterized by a constellation of clinical, histologic, immunologic and molecular findings. Many patients follow a slowly progressive, but indolent disease course, while others have a more aggressive disease. What incites the process and the factors that determine the subsequent biologic behavior remain largely unknown. This paper will explore the aspects of the disease that are generally accepted as fact and will consider some of the more speculative features of the process.