Nickel (Ni) is a naturally occurring element with numerous industrial applications such as in stainless steel, electroplating, pigments, and ceramics. As a result, anthropogenic Ni may enter the environment, resulting in locally elevated concentrations in soils. This chapter contains measurements of Ni levels in a variety of biota exposed to environmental contamination including plants, fungi, lichens, humans, and microbes. It may cause health issues in humans if its concentration increases more than normal. Acute inhalation exposure to Ni causes mucosal irritation, asthma, laryngeal cancer, kidney cancer, and cancer of the prostate or bones. Understanding molecular mechanisms in transgenic plants has enormous potential for improving Ni phytoremediation and microbial remediation efficiency. Ni does not bio-magnify in the terrestrial food web, except in hyperaccumulator plants, implying that toxicity to higher trophic levels is unlikely.