Detergents were administered intra-arterially to isolated arterially perfused eyes of rabbits and cats. Tween 80, Triton X-100, digitonin and sodium dodecyl sulphate (SDS) constricted uveal vessels and raised intraocular pressure (IOP) except for SDS which lowered IOP. Digitonin, a type B detergent was more active than three other detergents of type A. None of the four detergents did affect pupil size. After preconstriction with epinephrine low concentrations of nonionic detergents dilated uveal vessels but the fall in IOP by epinephrine was not affected; higher doses raised IOP. After preconstriction by eserine + Ach there were no effects of detergents on uveal flow and IOP. Mepacrine decreased the ocular effects of detergents suggesting that at least part of the effects from detergents is due to liberation of phospholipids.