Blends of poly(L-lactide) (PLLA) and poly(epsilon-caprolactone) (PCL) were prepared in a corotating twin screw miniextruder (40 rpm, 200 degrees). It was attempted to prepare multiblock copolymers by allowing a controlled number of transesterification reactions. Various catalysts (n-Bu(3)SnOMe, Sn(Oct)(2), Ti(OBu)(4), Y(Oct)(3), para-toluene sulphonic acid) were introduced to promote these transesterification reactions. However, PLLA degradation by ring-closing depolymerization was the dominant reaction in every case. Alternatively, after showing that L-lactide can be conveniently polymerized in the extruder, L-lactide and hydroxyl functionalized prepolymers of PCL or poly(ethylene glycol) (PEG) were fed to the extruder in the presence of stannous octoate. Monomer conversions of over 90% and effective transformation of all hydroxyl end groups present were generally reached. Di- and triblock copolymers could be prepared in this way with characteristics very similar to polymers prepared in a batch-type process, but with considerably reduced reaction times in a fashion, which is, in principle, scaleable to a continuous process for the production of such block copolymers.