Flexible PVC pellets were treated at 150-250 degrees C in 0-7M NaOH solutions for 0-12 h. The degree of dehydrochlorination of flexible PVC pellets increased with increasing reaction temperature and was about 100% at 250 degrees C over 5 h. A porous char, 2-16 mu m in pore size, was produced. The dehydrochlorination of PVC in the flexible PVC was proceeded by a first-order reaction in alkaline solution. The maximum rate of the dehydrochlorination for flexible PVC was reached at 5M NaOH. The apparent activation energies were 22-35 kcal/mol in 1-7M NaOH for flexible PVC.