The fundamental infrared absorption band of almost pure solid parahydrogen was investigated for evidence of quantum diffusion of orthohydrogen molecules. A feature of the band, involving a reorientation of neighboring o-H2 pairs, was observed to increase as a function of the time after solidification. The rate constant characterizing the diffusional formation of o-H2 pairs was found to lie in the range 0.3–0.7 h−1 for o-H2 concentrations of 0.7–1.6% and temperatures 1.14–2.10 K. The values and concentration dependence of the rate constant are in good agreement with the theory of Oyarzun and Van Kranendonk. The infrared data also agree within the experimental error with NMR observations of Amstutz, Thompson, and Meyer.