Objective      To prepare iloperidone sustained-release microspheres using polylactic-co-glycolic acid (PLGA) as sustained-release carrier and to study their release in vitro.       Methods        Iloperidone-containing PLGA microspheres were prepared by O/W emulsion-solvent evaporation method. The formulation and the preparation conditions were optimized by orthogonal tests. The morphology was evaluated by light microscopy. The particle size distribution was measured by Mastersizer 2000 (Malvern). The encapsulation efficiency and the drug load were assessed. The in vitro release characteristics of the microspheres were also assayed.       Results        The optimized preparation conditions were as follows: PLGA concentration 80 g/L

the volume ratio of oil to water 1∶30

polyvinyl alcohol concentration 1%

and speed of mechanical stirring 10 000 r/min. The results showed that iloperidone-containing PLGA microspheres were spherical in shape

with mean diameter of (24.56±0.46)μm

average encapsulation efficiency of (81.94±1.48)%

drug load of (7.50±0.13)%

and cumulative release of iloperidone from microspheres of 86.33% for 30 d.       Conclusion       Iloperidone-containing PLGA microspheres are prepared successfully by O/W emulsion-solvent evaporation method with high encapsulation efficiency

high drug load and good sustained release characteristics.