Abstract: An ignition timing control system for an internal combustion engine having a catalytic converter in its exhaust system and using a gasoline-alcohol blend fuel. Since the combustion temperature of the alcohols is lower than that of gasoline, the temperature of the exhaust gas decreases with increasing alcohol concentration of the fuel, which slows the heating of the catalyst and thus delays its activation, thereby degrading exhaust emission. In order to avoid this, ignition timing is retarded at cold engine starting with increasing alcohol concentration in the fuel so as to raise the exhaust gas temperature and promote the reactions in the catalytic converter. The retard amount is further adjusted by the manifold pressure and the intake air temperature.