Compounds characterized by a slow degradation rate in the environment, i.e. resistant to biodegradation, and photolysis processes, are classified as persistent and have often been considered as potential environmental problems. A more exacting approach recognizes that a compound released to the environment has a tendency to accumulate in one medium more than in others. Hence, partitioning, transport, and transformation rates of any particular compound will differ in each medium. Degradation processes in the dominant medium (where the compound is preferentially accumulated) are expected to have more effect on overall persistence of the measured compound than degradation processes in the other media. Photodegradation and biodegradation are the degradation processes which can naturaly clean up the environment. Biodegradation is expected to be the major mechanism of loss for most chemicals released into the environment. In this study, photodegradation and biodegradation processes of selected organic pollutants in different media have been reviewed.