Crystal growth rates of soluble and sparingly soluble salts were measured in a lean and dense fluidized-bed crystallizer, respectively, Then, the mass-transfer coefficients for crystal growth were determined using the two-step growth model. In the lean bed, the mass-transfer coefficient is independent of crystal size and solution velocity and is correlated with a form derived from the Froessling equation. In the dense bed, the mass-transfer coefficient is also fairly constant, which can be explained by a modified Froessling equation.