All are derived from hexachlorocyclopentadiene and have a similar structure based on two 3-dimensional carbon ring units, one of which is heavily chlorinated. WIth the exception of endosulfan, all are now banned in the US.
- Aldrin - Used mainly as an extremely persistent contact insecticide.
- Dieldrin - Very effective V's livestock ectoparasites (used in sheep dips).
- Endrin - General contact insecticide.
- Chlordane - Used to control earthworms in lawns & golf courses.