The pure rotational infrared absorption band of hydrogen has been investigated in the frequency region 500 to 1400 cm−1. Measurements have been made at densities of up to 100 amagat units and at temperatures of 298, 195, and 77 °K. A blue frequency shift, similar to the shift of the S(0) line observed by Bosomworth and Gush, of the S(1) line of 8 ± 3 cm−1 has been observed. An analysis of the profile has resulted in an individual S line profile which represents the high-frequency wing of the line by a "power law" rather than an exponential shape as presented previously by Bosomworth and Gush.