In selecting the title, it is recognized that melanosis in itself cannot be considered separately from many other intimately associated pathologic processes and that it probably rarely, if ever, occurs alone as a direct result of occupation. The scope of this study is concerned with the occupationally acquired dermatoses in which pigmentation due to increased melanin formation is an important or outstanding feature. Excluding the compensatory melanosis developing in response to undue exposure to sunlight or direct heat rays in otherwise normal persons in the course of their occupations, almost the entire group of conditions that may be classed under the foregoing title occurs in workers in petroleum or coal tar components or derivatives. In view of the constantly increasing diversity of these industries and the wide distribution of their products, the subject promises to become one of growing interest and importance. As early as 1876,