Abstract: The invention relates to a process for the preparation of methyl 1,1-dichloromethyl ether or of ethyl 1,1-dichloromethyl ether, according to which methyl formate or ethyl formate is reacted with phosgene, diphosgene, triphosgene or oxalyl chloride or one of their mixtures, at a temperature of between 40.degree. C. and 100.degree. C., in the presence of a catalyst chosen from the group consisting of trisubstituted phosphine oxides and sulphides, trisubstituted phosphine dichlorides, formamides, the products of reaction of formamides with chlorinating agents and mixtures thereof. The 1,1-dichloromethyl ethers are obtained in a high purity. They are useful especially for performing the formylation of aromatic compounds.