Polycondensation of diethoxydimethylsilane (DEDMS) in an active medium containing an excess of acetic acid was studied. It has been shown that the process selectivity could be well managed only if water was generated in the reaction mixture. We have found that both linear oligomers and cyclosiloxanes could be obtained with high selectivity and 80 % yield at least under conditions of the active medium. Further condensation of the linear oligomers led to the formation of α, ω-dihydroxypolydimethylsiloxanes with the molecular weight ranging from 3500 to 70000 Da. The obtained polydimethylsiloxane samples having hydroxyl end groups correspond to the industrial samples of liquid siloxane rubbers in terms of molecular weight parameters and virtually do not contain any low molecular cyclosiloxane impurities.