CaS:Bi, CaS:Ag, CaS:Pb, and Sr1-xCaxS nanocrystallites were synthesized via a solvothermal method at a relatively low temperature. The method is more environmentally friendly than traditional preparations (very little sulfur-based gases are formed and the method does not involve toxic H2S or CS2). Additionally, it is simple, convenient and produces a good yield. The products with an average diam of 30-100 nm were stable at humid air. The emission color of Sr1-xCaxS nanocrystallites varied from blue (SrS) to red (Sr0.6Ca0.4S). The emitted light of CaS:Bi, CaS:Ag and CaS:Pb nanocrystallites are blue, red, and blue, respectively. (C) 2003 The Electrochemical Society.