In present study, three new spectrophotometric methods, original UV spectrophotometry, first and second order derivative UV spectrophotometry and a new liquid chromatographic method were developed for the determination of acemetacin in pharmaceutical preparations. In original UV spectrophotometry, absorbances were measured at 280,0 nm in the zero order UV spectra of the solution of acemetacin in O,1N NaOH in the range of 210 - 325 nm. In first derivative UV spectrophotometry, dA/dX values were measured at 240.0 nm in the first derivative UV spectra of the solution of acemetacin in 0,1 N NaOH in the range of 230 - 325 nm (AX= 2 nm). In second derivative UV spectrophotometry d2A/dA2 values were measured at 274.0 nm in the second derivative UV spectra of the solution of acemetacin in 0,1 NNaOH in the range of 240 - 325 nm (AX= 2 nm). Linearity range was found as 8.0 - 85.0 jUg/mL in original UV spectrophotometric and first order derivative UV spectrophotometric methods and 15.0 — 85.0 jUg/mL in second order derivative UV spectrophotometric method. Mean recoveries and the relative standard deviations of the methods were found as 100.64 % and 0.95 % in original UV spectrophotometic method 100.36 % and 0.62 % in first derivative UV spectrophotometric method and, 100.45 % and 1.10 % in second derivative UV spectrophotometric method respectively. Also, a new HPLC method was developed. In this method, ACE C18 analytical column and a mobile phase composed of acetonitrile - water (80:20, v/v) at a flow rate of 1.0 mL/min was used for the optimal chromatographic separation using UV detection at 280 nm. Dienogest was used as internal standard. All the methods developed were successfully applied to two tablet formulations commercially available in Turkish drug market. All the results were compared statistically with each other.