Abstract: A new process is disclosed for the synthesis of alkylene carbonates having from 2 to 4 carbon atoms in the chain, starting from a corresponding halohydrin having the formula: ##STR1## wherein R.sub.a, R.sub.b, R.sub.c and R.sub.d are independently hydrogen or alkyl, aryl, alkylaryl or arylalkyl radicals and where X is a halogen, characterized in that said halohydrin is reacted with a bicarbonate of a quaternary -onium compound, where "-onium" means ammonium, phosphonium, arsonium or stibonium, preferably using an organic solvent as diluent and operating in the presence of carbon dioxide.