Composite ultrafine fibers of hydrogel/polylactide copolymer were successfully electrospun from water-in-oil suspensions. Effects of the suspension composition on the morphology and microstructure of the obtained fibers were investigated, including both aqueous phase and oily phase, that is, hydrogel (chitosan or gelatin), polylactide copolymers [poly(ethylene glycol)-b-poly (L-lactide-co-caprolactone) (PELCL) or poly(L-lactide-co-glycolide) (PLGA)], organic solvents and surfactants. Scanning electron micrographs showed that mixed solvents of chloroform and N,N-dimethyl formamide or 2,2,2-trifluoroethanol were preferred to form beads-free ultrafine fibers with diameter in the range of 230-470 nm. With ethyl acetate as organic solvent, compared with chitosan hydrogel/PELCL composite fibers, chitosan hydrogel/PLGA fibers showed narrower distribution of diameter in 230-590 nm. Different hydrogel and surfactants used in this experiment had slight effects on the morphology of the obtained fibers, whereas transmission electron micrographs exhibited chitosan and gelatin hydrogel could be in situ encapsulated in the fibers discontinuously. This method may promise a new aqueous reservoir for encapsulation and controlled release of bioactive agents. POLYM. ENG. SCI., 52:2695-2704, 2012. (C) 2012 Society of Plastics Engineers