The present invention provides a biodegradable drug delivery compositioncomprising: (i) a mixture of at least threedifferent block copolymers, wherein each block copolymer is: (a) abiodegradable triblock copolymer having the formula: A v-B w-A xwherein A is a polyester and B is polyethylene glycol and v and x are thenumber of repeat units from 1 to 3,000 and w is the numberof repeat units from 3 to 300 and v=x or v.noteq.x； or (b) a biodegradablediblock copolymer having the formula: C y-A z wherein A is apolyester and C is an end-capped polyethylene glycol and y and z are thenumber of repeat units with y = 2 to 250 and z = 1 to 3,000；and wherein the mixture comprises at least one (a) and at least one (b)； andthe weight ratio between (a) and (b) is 1:19 to 5:1； and(ii) at least one pharmaceutically active ingredient.[Continued on next page]
