In this review, we will give a brief overview of recent (year 2000 or later) examples of the photochemical reactions in alternative media. e word “alternative” is rather ambiguous, but we herein deal with any photochemistry that is conducted in organized, but dimensionally not well-dened, media. e photochemistry in well-organized media, such as supramolecular hosts and crystals, will be reviewed in other chapters. e less organized “alternative” media include supercritical uids, voids in polymer and related lms, ionic liquids, liquid crystals, organogels, microemulsions, micelles, vesicles, and passive voids in dendrimers and so on, which have been extensively exploited as unique media for photophysical and photochemical studies.1 We will focus mostly on the photochemistry in such alternative media with only occasional reference to the photophysics. Because of the diversity and vagueness of the topics, the chapter will not be comprehensive; rather, we will discuss the current status and characteristics of photochemistry in alternative media by illustrating representative examples.