Cyanides are among the most acutely toxic of all industrial chemicals and are produced in large quantities and used in many different applications. However, they cause few serious accidents or deaths. This is partly because the word cyanide is synonymous with a highly poisonous substance and a certain amount of care in handling is thereby ensured. The cyanides and nitriles are a disparate group of substances characterized by the presence of a cyanide (CN) group in their molecular structure. The cyanide group consists of a carbon bonded to a nitrogen. In those cases where the cyanide group is readily available, their toxicity is likely to have similarity to hydrogen cyanide (HCN). The chemical and physical characteristics of the compound will affect the potential availability of the cyanide group and therefore the hazards associated with different chemical species. For purposes of the toxicologist, cyanides and nitriles can be classified into the following groups: The inorganic cyanides include (Group 1) hydrogen cyanide, cyanogen, simple salts of hydrogen cyanide that dissociate readily to release CN−1 ions (such as sodium, potassium, calcium, and ammonium cyanide); (Group 2) halogenated compounds such as cyanogen chloride or bromide; and (Group 3) simple and complex salts of hydrogen cyanide that do not dissociate readily to release CN−1 ions (such as cobalt cyanide trihydrate, cupric and cuprous cyanide, silver cyanide, and ferricyanide and ferrocyanide salts). The organic cyanides include (Group 4) cyanide glycosides produced by plants (such as amygdalin and linamarin); and (Group 5) nitriles [such as acetonitrile (methyl cyanide), acrylonitrile and isobutyronitrile]. Keywords: Cyanides; Nitriles; Bhopal; India; Methylisocyanate release