Cadmium selenide (CdSe) quantum dots were prepared in high-temperature water via a rapid hot-injection method intended to mimic conventional synthesis in organic solvents. The nanocrystals were smaller than those previously produced hydrothermally under nonisothermal conditions when using the same process parameters. It is possible that the nucleation and growth events were greatly influenced by the present injection method. In general, the physical and optical properties of the nanocrystals were influenced by the experimental conditions. Variations in reaction temperature (200-240 degrees C), reaction time (1-10 min), pH (7-11), Cd:Se molar ratio (4:1-40:1) and Cd:stabilizer molar ratio (0.24-1.18) affected the mean particle size, distribution of sizes, and quantum yield. As-prepared nanoparticles exhibited quantum yields in excess of 5%.