Application of fuzzy logic to control of moisture content during fluidized bed granulation is described. To avoid overshoot and to maintain control stability, a linguistic algorithm employing IF-THEN rules, with process lag element taken into consideration, was constructed using moisture content and its changing rate as input variables. Good response and stability without overshoot, which had been impossible to attain with conventional techniques, were achieved by adopting the developed systems. This system also maintained stability by favorable response to rapid increase in fluidization air velocity during operation.