Optically active polymers that are composed of monomer residues derived from chiral pre-polymerized monomers, which maintain the chirality of the pre-polymerized monomers upon polymerization are disclosed. These polymers can be composed of monomer residues that are derived from readily available chiral monomers and can be designed to have pre-determined characteristics such as chirality, biodegradability and functionality. Uses of these polymers as therapeutically active agents, and/or as carriers of therapeutically active agents, for delivering the active agents to a targeted bodily site and/or for a sustained release of the active agent, are further disclosed. Also disclosed are processed of preparing the polymers, compositions and medical devices containing the polymers, and conjugates of these polymers and various agents.