Candida antarctica lipase B (CALB) was found to be an efficient catalyst for copolymerization of diesters with amino-substituted diols to form poly(amine-co-esters) in one step. The copolymerization reactions were carried out at 50-100 degrees C in two stages: first stage oligomerization under 1 atm pressure of nitrogen followed by second stage polymerization under 1-2 mmHg vacuum. The formed copolymers possessed molecular weight (M(w)) up to 59000 and typical polydispersity (M(w)/M(n)) between 1.5 and 2.3. The enzymatic reaction appears to be quite general and accommodates a large number of comonomer substrates with various chain length and substituents. Thus, C(4)-C(12) diesters (i.e., from succinate to dodecanedioate) and diethanolamine comonomers with either an alkyl (methyl, ethyl, n-butyl, t-butyl) or an aryl (phenyl) substituent on nitrogen were successfully incorporated into the poly(amine-co-ester) chains. Biodegradable polyesters bearing tertiary amino groups have been reported to be efficient carriers for gene delivery. The high tolerance of the lipase toward tertiary amino functional groups as described in this paper provides new routes for synthesizing poly(amine-co-esters) with tailored structures for specific biomedical applications.