The spatial instability of an incompressible liquid sheet injected into a compressible gas is investigated, The evolution of both symmetrical and antisymmetrical disturbances is considered. It is found that the growth rate of disturbances increases initially with gas compressibility, reaches a maximum near gas Mach number 1, and then decreases as the gas Mach number is increased further. The antisymmetrical disturbances prevail over symmetrical disturbances when the wavelength is large while both types of disturbances grow at approximately the same rate for short waves. The results are compared with the temporal instability analysis of Ibrahim, The similarities and dissimilarities between the present findings and Li and Kelly’s are elucidated.