The significance of this research and development program is the demonstrated feasibility of fabricating large infrared transmitting windows of zinc sulfide with good physical charcteristics by the chemical vapor deposition CVD process. Plates approximately 1 ft X 2 ft with good transmission between 8 and 12 micrometers were made and delivered as window blanks. Furthermore, the imaging properties of CVD ZnS, particularly in the visible end of the spectrum were significantly improved in comparison to material fabricated during an earlier program. It was also shown that it may be possible to extend the useful transmission range of zinc sulfide by fabricating a solid solution with zinc selenide. Material fabricated during this program had a transmittance in excess of 60 from 6 to 12.5 micrometers, a flexural strength of 15,000 psi, and a use limit above 200 C. The potential for improving the optical quality of the material through better control of the process andor annealing the material after deposition was also demonstrated.