The present invention provides an amphiphilic polysiloxane prepolymer which comprises hydrophilic monomeric units derived from at least one hydrophilic vinylic monomer, polysiloxane crosslinking units derived from at least one polysiloxane crosslinker having at least two terminal ethylenically-unsaturated groups, dangling polysiloxane chains each of which is terminated with one ethylenically unsaturated group, and chain-transfer units derived from a chain transfer agent other than a RAFT agent. A prepolymer of the invention is suitable for making hydrogel contact lenses. The present invention is also related to hydrogel contact lenses made from an amphiphilic polysiloxane prepolymer of the invention and to processes for preparing an amphiphilic polysiloxane prepolymer of the invention and for making silicone hydrogel contact lenses.