Infrared (IR) absorption spectra of pyrochlore-type Ca2+-doped La2Zr2O7 proton conductors, i.e., (La2-xCax)Zr2O7-delta and La-2(Zr2-xCax)O7-delta systems, were studied by the diffuse reflection method. The O-H stretching vibrations (v(OH)) due to the protons dissolved in the crystal with negligible effects of adhesion and/or adsorption water could be detected by improvement of the sample preparation and the diffuse reflection technique. The v(OH) bands, due to protons dissolved in the crystal, were distinctly different between the (La2-xCax)Zr2O7-delta and the La-2(Zr2-xCax)O7-delta systems; three v(OH) bands at 3517, 3401, and 3323 cm(-1) for the (La2-xCax)Zr2O7-delta system and six v(OH) bands at 3517, 3430, 3414, 3371, 3341, and 3289 cm 21 for the La-2(Zr2-xCax)O7-delta system were observed. The stable sites for dissolved protons were distinctly different between the two systems. The wave numbers and the widths of the v(OH) bands were higher and much sharper than those reported for the well-known perovskite-related-type proton conductors. It was concluded that the O-H bonds in Ca2+-doped La-2 Zr2O7 crystal are tight compared with perovskite-related-type proton conductors, and that definite stable sites for protons exist in Ca2+-doped La2Zr2O7 crystal. In the IR spectra of (La2-xCax)Zr2O7-delta samples with various water vapor pressures, p(H2O), of proton dissolution treatment, the preferred dissolution of protons into the specific site was observed under low p(H2O) atmosphere. The details of the dissolution environment of protons are also discussed.