The theory of scattering of plane waves of sound is extended to scatterers in the form of thin elastic shells of cylindrical and spherical shape. As for all elastic scatterers, the scattering action is the resultant of (1) “rigid body scattering,” i.e., the scattering which would be present if the scatterer were rigid and immovable; (2) “radiation scattering,” which represents the sound radiation from the shell undergoing forced vibrations under the influence of the incident wave pressure and which is determined by the dynamic characteristics of the submerged shell. Contrarily to solid scatterers whose dynamic characteristics are little differentin vacuoand in the fluid medium, the characteristics of shells are profoundly altered by fluid reaction. When the shell is excited near resonance, the scattering pattern resembles the dynamic response of the shell in that it is highly frequency sensitive.