We present a model of bicontinuous microemulsion structure based on a disordered lamellar structure. The scattering predicted by this model is compared with measured small angle neutron scattering curves from a family of microemulsions formed with sodium 4-(1′-heptylnonyl) benzenesulfonate, iso-butanol, D2O brines, and the even alkanes from octane to hexadecane. The model, with two parameters, fits the data on an absolute scale well. Disordered lamellae spacings and distortion lengths vary from approximately 850 and 570 Aring;, respectively, for microemulsions formed with dodecane to 430 and 400 Å for those formed with hexadecane. A distribution of lamellae thicknesses can be introduced to account for scattering curves that display a maximum in intensity scattered at zero scattering vector.