Ag2Se　nanocrystals　were　rapidly　synthesized　by　the　sonochemical　reaction　between　Ag　ions　and　Se　powders　in　diluted　ammonia　water.　By　using　different　complexing　agents　(NH3,　citric　acid　or　KSCN)　in　the　reaction　system,　Ag2Se　nano-spheres　with　different　sizes　were　obtained.　X-ray　diffraction　patterns　showed　that　the　samples　obtained　was　orthorhombic　beta-Ag2Se.　The　morphology　was　characterized　by　scanning　electron　microscopy　(SEM).　This　mild　method　may　be　extended　to　prepare　other　chalcogenides　nanocrystalline　at　room　temperature.　(c)　2006　Elsevier　B.V.　All　rights　reserved.