The crystal growth rates of potassium sulfate were measured in a relatively low temperature range from 0 to 35degreesC. The temperature dependence of the growth rate was examined because of the lack of rate data at low temperatures. A minimum growth rate was found at nearly 20degreesC. The reason why the growth rate increased at a low temperature of less than 20degreesC is that 'fine crystals' might already exist in a supersaturated solution of potassium sulfate before crystallization and that deposition of these fine crystals on the seed crystal surface may enhance the crystal growth rate. The existence of the fine crystals in supersaturated solution was confirmed by measuring the density and electric conductivity of the mother liquor of potassium sulfate.