To obtain the subject polyester composed of recurring units of each specific structure, and usable in surgery devices, for example, suture threads, forming devices, drug delivery matrices.

This polyester comprises a crosslinked form of a polyester composed of a 1st divalent recurring unit of the formula (R1 and R2 are each H or a 1-8C alkyl; R3 is a 2-12C alkylene, etc.) and a 2nd recurring unit selected from the group consisting of units of the formula [-O-R12-]u{R12 is a 2-8C alkylene containing internal amine [-N(R10)](R10 is H or a 1-8C alkyl) or amido [-N(R11)-] (R11 is the same as R10 independently); (u) is an integer of 1 to about 2,000}, and, as circumstances require, a 3rd recurring unit selected from respective units of the formulae [-O-R4]A(R4 is a 2-8C alkylene; A is same as (u)), [-O-R5-C(O)-]B (R5 is CH2-CH2-O-CH2, etc.; B is such an integer of 1-n as to afford a number-average molecular weight of about below 200,000), etc.