Poly(vinyl chloride) (PVC) can be extensively dehydrochlorinated by KOH at room temperature in a mixed homogeneous medium of tetrahydrofuran (TI-IF) and poly(ethylene glycol) (PEG) with a number average molar mass greater than 200 g mol(-1). PEGs act as solubility promoters for the base and highly active catalyst for the reaction. The structure of dehydrochlorinated PVC (DPVC) has been studied by elemental analysis, UV/visible, FT-infrarcd, FT-Raman and X-ray photon electron spectroscopies. Experimental results demonstrated that the reaction was nearly finished within 1 h and had a conversion of 84-98%. DPVCs have high concentrations of long polyene sequences and can be doped by iodine.