Chloroform, a heavy, transparent, colorless liquid compound composed of carbon, hydrogen, and chlorine. Chloroform vaporizes easily and has a strong, sweet odor. It does not dissolve in water, but is soluble in organic solvents such as alcohol and ether. Chloroform must be kept in the dark or it will decompose into highly poisonous phosgene. Chloroform is manufactured by the chlorination of ethyl alcohol or methane.

Chloroform is used as a general solvent. It is also used in fumigants and insecticides. Chloroform is a potent general anesthetic; when inhaled, it acts on the central nervous system and the patient quickly becomes unconscious. But because it can cause severe damage to internal organs—especially the heart, liver, and kidneys—chloroform is no longer used medically.

Chloroform was first used as an anesthetic in 1847 by Sir James Y. Simpson, a Scottish physician. It remained in use, in obstetrics and surgery, for many years until the development of anesthetics with less dangerous side effects.

The chemical formula for chloroform is CHCl3.