Cyhalothrin is formed by esterifying 3-(2-chloro-3,3,3-trifluoroprop-1-enyl)-2,2- dimethylcyclopropanecarboxylic acid with alpha-cyano-3-phenoxybenzyl alcohol, and it consists of a mixture of four stereoisomers. Lambda-cyhalothrin consists of one enantiomeric pair of isomers and is the more biologically active form.