Organic isocyanates are continuously prepared by reacting primary organic amines with phosgene in the presence of an inert, organic solvent, with the reaction mixture being circulated by means of a bubble column at a temperature of from 60.degree. to 100.degree. C. and with the ratio of the quantity of the circulated amine reaction products to the quantity of the amine supplied of from 100:1 to 5:1.