The issues considered relate to the dynamics of harm in terms of distinguishing legal from illegal uses of the environment, the conceptualization of an eco-global criminology, practical problems of data collection, various types of knowledge production and collection, and the politics of researching transnational environmental harm. In discussing environmental harm and the legal-illegal divide, the article describes illegal practices within the legitimate environmental enterprises of logging, wildlife exports, lobster fishing, and fishing in general. The paper notes that a licit market is state-regulated, open to public scrutiny, and based upon legal activities; whereas an illicit market is unregulated, untaxed, and part of a hidden or "black" economy. Licit and illicit markets can share the same practices and the same people driven by the same economic motives. In the discussion of the conceptualization of "eco-global criminology," the article refers to a criminological approach that is informed by ecological considerations and by a critical analysis that is worldwide in scale and perspective. Eco-global criminology is based on eco-justice concepts of harm that include consideration of transgressions against environments, nonhuman species, and humans. The focus is on the harm caused by a particular activity. This is followed by a section that addresses research on transnational environmental harms, including the practical, scientific, and political challenges involved. Research issues discussed are DNA testing, satellite surveillance, automated video monitoring, and environmental forensics. The article concludes with a discussion of the "politics of knowing and knowledge." This pertains to contested scientific evidence used in investigations of environmental harm and who is qualified and accepted as a "scientific expert." 44 references