In the literature the construction of some high pressure infrared gas cells has been described. However, these cells show, just as the commercially available high pressure gas cells, many problems with the cell windows. For our research on infrared integrated intensities we needed reliable pressure cells, which could be used at pressures up to 90 atm and at temperatures up to 150°C. As reliable cells fulfilling both conditions simultaneously can practically not be made, two cells were designed, one with maximum operating conditions: 90 atm at 50°C; the other, 150°C at 20 atm. Besides, attention was given to the additional requirements of large window aperture and optical path length. Recent developments in the construction of window sealings for high pressure infrared liquid cells were succesfully applied to the construction of the gas cells.