Growth rates of boric acid crystals have been measured both in pure aqueous solution and under the influence of electrical field as a function of supersaturation and electrical field intensity in a laboratory scale fluidized bed crystallizer at the temperature of 30degreesC. The effect of electrical field was estimated from the growth rate data to evaluate the relative magnitude of two resistances, diffusion and integration. In absence of electrical field, the obtained results indicate that the controlling mechanism is mainly integration. However, in presence of electrical field, growth rate of boric acid were controlled by diffusion and reaction steps. In the absence of electrical field, boric acid crystals grow dendritically at any level of supersaturation from pure boric acid solution. In case of electrical field, the dendritic structure was depressed.