Degradable aliphatic polyesters present great interest as scaffold in tissue engineering. During the past decade, important advances have been accomplished in the understanding of the degradation behaviors of aliphatic polyesters derived from lactic acids, glycolic acid and e-caprolactone. Degradation of large-size polymers is autocatalyzed by carboxyl endgroups initially present or generated by ester bond cleavage. Faster internal degradation and degradation-induced morphological and compositional changes are three of the most important findings deduced from the behaviors of various aliphatic polyesters. This chapter is aimed at presenting the state-of-the-art in this domain. Efforts are focused on detailing the degradation mechanism and the effects of various factors on the degradation behaviors of these polymers.