A powder x-ray diffraction technique has been developed for the quantification of carbamazepine in tablets. The other tablet ingredients were microcrystalline cellulose, starch, stearic acid and silicon dioxide. The tablets were ground in a ball mill and the powder mixed with lithium fluoride (20% w/w) which was the internal standard. Five lines of carbamazepine with d-spacings of 3.38, 3.34, 3.28, 3.26 and 3.23 Å and the 2.01 Å line of lithium fluoride were used for the quantitative analysis. A plot of the intensity ratio (sum of the intensities of the lines of carbamazepine/intensity of die lithium fluoride line) as a function of the weight fraction of carbamazepine in the tablets resulted in a straight line. Using this standard curve, the carbamazepine content in “unknown” tablets was determined and ranged between 98.6 and 101.6% of the actual drug content. The coefficient of variation in the determinations ranged between 0.28 and 2.1%.