The occurrence, chemistry, and speciation of rhenium (Re) in environmental components such as soil and water, as well as rhenium separation and analytical characterization techniques in the environment, are summarized. Rhenium has two isotopes: one is stable
185
Re and the other is radioactive
187
Re, which has a very long half‐life of 4.35 × 10
10
years. The decay system,
187
Re–
187
Os has been used for dating rocks and meteorites. Artificially made radioisotopes with short half‐lives, such as
186
Re and
188
Re have been used in radiopharmaceuticals. Because of similarities in chemistry, rhenium has been used as a chemical analog of technetium.