The coupling loss factor is a parameter which is unique to Statistical Energy Analysis. Power transmission between two subsystems is expressed in terms of the coupling loss factor. CLFs can refer to bending@ longitudinal and shear waves@ although bending wave propagation is mostly considered. CLFs discussed in this Item include power transmission between beams and plates@ either in line or at right angles. For plates at right angles both normal incidence and random incidence are considered. CLFs are significant for power transmission from structures@ such as plates and cylinders@ to acoustic spaces. Power transmission from structures to acoustic spaces involves the radiation efficiency of the structure. Radiation efficiencies of plates and cylinders are discussed