The degradation of two series of copolymers made of 1,5-dioxepan-2-one (DXO) and L- or D,L-dilactide has been investigated. In vitro degradation of the six copolymers with different ratios of the ingoing components was followed using size exlusion chromatography (SEC), nuclear magnetic resonance (NMR) spectrometry, Fourier transform infrared (FTIR) spectroscopy, and differential scanning calorimetry (DSC). The copolymers with a high content of lactic acid units showed a higher rate of hydrolysis than the DXO-rich copolymers. The copolymer morphology also affects the rate of degradation as seen in the differences between amorphous and semicrystalline samples. The effect of electron beam sterilization was studied as well as the degradation products formed using the gas chromatography-mass spectrometry (GC-MS) technique. The major degradation products resulted from ester bond cleavage. Kinetics of the in vitro degradation indicate a complex hydrolysis, probably a mixture of an uncatalyzed and catalyzed mechanism.