The results of this study indicate that the addition of low concentrations of a nonionic detergent such as those represented by the Tween, Brij, or Triton classes causes an apparent activation of nitric oxide synthase. It is possible that this apparent activation is due to the ability of these detergents to stabilize the protein. The stabilizing influence of the detergents may be a result of inhibiting the dissociation of the dimeric protein into monomers or the dissociation of an essential cofactor or prosthetic group from the active enzyme. Regardless of the mechanism of action, the addition of low concentrations of nonionic detergents results in longer and increased nitric oxide synthase activity and may be an important tool for those involved in enzymological studies of nitric oxide synthase.