Aromatic polycarbonates are prepared by a process which includes a continuous stage of oligomer preparation from a carbonyl halide such as phosgene and a dihydroxyaromatic compound such as bisphenol A, under interfacial conditions in the presence of an interfacial polycarbonate formation catalyst and an alkali metal hydroxide. The molar ratio of alkali metal hydroxide to carbonyl halide during oligomer preparation is up to 1.8:1, preferably in the range of about 1.45-1.8:1. The oligomeric intermediate product is then converted to high molecular weight polycarbonate having a low proportion of cyclic oligomers, which improves its thermodynamic stability.