A CW transverse-flow chemical CO laser based on the CS+O→CO+S(+75-kcal/mole) reaction has been studied. Power output is 4.5 W with a gas flow of 70 l/min at 5.4 torr. The output occurs in the 3-2 to 14-13 vibrational transitions. Gain measurements have been made for a number of lines. The maximum observed gain coefficient is 0.006 cm-1. The variation of the laser output with a number of parameters including the distance between CS2 injection and the optical cavity axis is also reported.