This paper reports a study about the determination of inorganic constituents (calcium, magnesium, potassium, sulfur (as sulfate) and phosphurus (as phosphate) in sugar cane juice, vinasse and molasses. Two techniques for organic matter oxidation were studied: wet and dry digestion. The data obtained showed that for these determinations any of these procedures can be employed, excepting the sulfur determination in molasses which must be made be wet digestion. The proposed techniques employ analytical methods acessible to most laboratories and permit fast and accurate determination of the five inorganic constituents.