Reverse micelles and w/o microemulsions of three of the individual separated polyoxyethylene p-tert-octylphenyl ether (OPEn, n = 5, 7, and 9) components of Triton X-100 are investigated in cyclohexane by controlled partial pressure-vapor pressure osmometry (CPP-VPO), dynamic light scattering, and transient electric birefringence methods. The mean aggregation number N, apparent hydrodynamic diameter D-h and the probable shape of the aggregates are determined as a function of water content w(o), temperature, and the concentrations of the surfactant and a cosurfactant (n-hexanol), if added, The effects of the length of the hydrophilic chain of the surfactant and the presence of a cosurfactant (n-hexanol) on the equilibrium properties and dynamic behavior of the aggregates are discussed.