A theoretical analysis of the power generated by a pneumatic type wave-energy conversion buoy is presented. Results obtained from the analysis show tha the peak-power value occurs at the resonant period of the buoy-water column system and not at the natural heaving period, as was previosuly assumed. A secondary peak occurs at the resonant period of the center pipe which is in free communication with the water. This resonance is similar to that of a surge chamber. The power converted by the buoy is shown to be proportional to the cube of the wave height. The length of the center pipe is shown to have an optimum value for which a maximum power is obtained at a given resonant wave period. This length corresponds to that of the water mass in the center pipe, which is approximately two-thirds of the sum of the buoy mass and the added mass.