A series of novel biodegradable hydrogels were designed and synthesized from four types of unsaturated poly(ester amide) (UPEA) and poly(ethylene glycol) diacrylate (PEG-DA) precursors by UV photocrosslinking. These newly synthesized biodegradable UPEA/PEG-DA hydrogels were characterized by their gel fraction (G(f)), equilibrium swelling ratio (Q(eq)), compressive modulus, and interior morphology. The effect of the precursor feed ratio (UPEAs to PEG-DA) on the properties of the hydrogels was also studied. The incorporation of UPEA polymers into the PEG-DA hydrogels increased their hydrophobicity, crosslinking density (denser network), and mechanical strength (higher compressive modulus) but reduced Qeq. When different types of UPEA precursors were coupled with PEG-DA at the same feed ratio (20 wt %), the resulting hydrogels had similar Q(eq) values and porous three-dimensional interior morphologies but different Gf and compressive modulus values. These differences in the hydrogel properties were correlated to the chemical structures of the UPEA precursors; that is, the different locations of the > C=C < double bonds in individual UPEA segments resulted in their different reactivities toward PEG-DA to form hydrogels. (c) 2005 Wiley Periodicals, Inc.