Cyphenothrin (d-t-Cyphenothrin, d-Cyphenothrin, Cyano(3-phenoxyphenyl)methyl 2,2-dimethyl-3-(2-methylprop-1-en-1-yl)cyclopropanecarboxylate, CAS#39515-40-7) is a synthetic pyrethroid insecticide. It is effective against cockroaches that have developed resistance to organophosphorous and carbamate insecticides.
As a Synthetic pyrethroid, cyphenothrin acts by contact or by ingestion and is not a systemic pesticide. 　　　　Cyphenothrin reaches the nerve-endings of pests and causes the interruption of communication with the brain. After a period of excitation and convulsions, pests are paralyzed(knockdown) and then they die. The addition of tetramentrin and bioallethrin reduces the recovery ability of pests, and consequently improves the efficacy of cyphenothrin.

Cyphenothrin is a potent pesticide with contact and stomach, good residual activity and a mild knockdown against fly, mosquito, roach and other pests in public, industrial area and household. It has spectacular expelling action to big roach such as periplaneta fuliginose and periplaneta Americana.
It is also ideal for control and prevention of insects that attack ood and fabric.

Due to its rapid photodegradation and its low mammalian toxicity. Cyphenothrin is particularly suitable for use in household pesticides and for indoor pest control, as well as Public Health pests.

In housefly at 0.005-0.05% and alluring activity at 0.0005-0.001%. It is better than permethrin, fenpropathrin, prallethrin and d-phenothrin in prevention of wool and fur pests such as grain moth and achieves best in mosquito-repellent test by dipping mosquito net in liquids of d-phenothrin, permethrin, fenpropathrin and fenvalerate respectively.