Raman scattering and X-ray diffraction measurements were made to identify stage structure of CsC24(C2H4)nand CsC24(C2H3CN)n, which were exposed to air for a long time. Their electric conductivities were also measured during the long exposure to air. Raman spectra suggest that the gradual degradation of their electric conductivities in air is caused by the slow decomposition of the ternary GIC's from the periphery region, although results of X-ray diffraction for all samples indicate the retention of the initial stage structure. Among the samples, CsC24(C2H4)1.4which absorbed large amount of ethylene, was found to be exceptionally stable both in its stage structure and electric conductivity.