This discipline involves the study of organic compounds in the geosphere, both natural and pollutants, with the aim of achieving information on the basic processes for ecosystem functioning, evolution and anthropogenic disturbances. This wide topic allows the study of a large diversity of subjects: marine and terrestrial systems, ancient and recent environments, deleterious effects on ecosystems, animal and human populations, environmental and climatic change. In order to approach these topics, studies on sediments, water, air, atmospheric deposition, snow, soil, organisms (vegetal and animal), food and human fluids have been performed. To this end, diverse sampling methods have been developed and specific studies have been devoted to analytical techniques such as chromatography and mass spectrometry. The topics under development at present are: long-range transport of organic pollutants paleoceanography toxic effects of organic trace pollutants in humans and higher organisms organic markers of algal and microbial activity in recent aquatic ecosystems crude oil degradation processes