A process for the production of polysiloxane/polycarbonate block cocondensation products is disclosed. The process comprises reacting in the melt at temperatures of 250 to 320.degree. C. and pressures of 0.01 to 100 mbar (a) a hydroxyaryloxy-terminated dimethylsiloxane with (b) an oligocarbonate. The oligocarbonate is characterized in that its weight average molecular weight is 3000 to 24000 and the molar ratio of its OH end groups to aryl end groups is 10:90 to 70:30. The weight ratio of said (a) to said (b) in the inventive process is between 1:99 and 40:60. Also disclosed are the products prepared by the process.