In the preparation of ZnS and CdS fine particles by an ultrasonic spray-pyrolysis method, the particle size was changed from submicrometre to micrometre size by changing the concentration of the metal nitrates in the starting aqueous solution containing Zn(NO3)(2) or Cd(NO3)(2) and SC(NH2)(2). The effects of temperature profile in the reactor furnace on the properties of prepared particles were also investigated by varying the temperature profiles : constant and increasing temperature distributions. The volume mean diameter of the prepared particles was found to be approximately proportional to the one-third power of the concentration of the metal nitrates in the solution. The crystalline phase and fluorescence properties of ZnS and CdS particles did not depend on the particle size.