Methyl isothiocyanate (MITC; CAS: 556-61-6) is a colorless crystalline solid used primarily as a component of pesticides applied as soil fumigants. MITC injected into soil rapidly vaporizes. MITC is a potent, direct-acting irritant to the eyes and respiratory tract. It is completely absorbed following oral exposure and accumulates in the thyroid, liver, kidneys, whole blood, and adrenals. Exposure to MITC has the potential to cause nasal and lung lesions. Review of available studies indicates that MITC is not a reproductive/developmental toxicant, is not mutagenic or genotoxic, and not likely to be carcinogenic. However, it has the potential to be immunotoxic.