Experimental results for the pyroelectric coefficient, Curie temperature, dielectric constant, and loss tangent of (ND2CD2COOD)3D2SO4 were obtained and compared with (ND2CH2COOD)3D2SO4 and (NH2CH2COOH)3H2SO4. It is shown that complete deuteration of TGS does not result in an improved pyroelectric detector material since further substitution of deuterium for hydrogen in the -CH2- radical does not apparently contribute to the spontaneous polarization of deuterated TGS.