The present analysis substantially improves the spectroscopic characterization of near infrared OCS in a window region (3850-4200 cm À1 ) important for atmospheric studies of Venus. Previous studies in this spectral region cataloged numerous OCS line positions, but accurate line intensities were measured for only three strong bands. In this paper, the corresponding line intensities are obtained for 41 OCS bands, including weak isotopic bands reported for the first time. The 2n 3 (0002-0000) band is analyzed for 10 OCS isotopologues (adding 16 O 13 C 34 S, 17 O 12 C 32 S, 16 O 12 C 36 S, 18 O 12 C 34 S, and 16 O 13 C 33 S). In addition, observations of 0332-0330 of the main isotope, 16 O 12 C 32 S, provides accurate vibration-rotation parameters for the upper state (and the lower state, 0330 of 16 O 12 C 32 S). Finally, one unidentified band is seen at 3969.3 cm À1 ; its lower state is clearly the ground state of 16 O 12 C 32 S. The line strengths of these seven previously unanalyzed bands plus 34 other bands of the OCS isotopologues, 16 O 12 C 32 S, 16 O 12 C 34 S, 16 O 13 C 32 S, 16 O 12 C 33 S, and 18 O 12 C 32 S, were least-squares fitted to determine strength parameters, S v and Herman-Wallis coefficients. Finally, the intensities of 17 additional very weak bands were estimated to provide an extensive new database of OCS line parameters to support remote sensing of Venus. The integrated intensity in cm À1 / (molecule cm À2 ) at 296 K is 8.1 Â10 À19 for the 3800-4200 cm À1 region.