A fluorimetric method was developed for the determination of baclofen by means of the derivative formed with 4-chloro-7-nitrobenzofurazan (NBD-Cl). The reaction proceeds quantitatively at pH 9–9.5 and 60 °C in 45 min when the molar ratio of reagent to baclofen is 20. After the extraction of the derivative with ethyl acetate, the fluorescence intensity was measured at 525 nm using the mercury line at 436 nm (filter) for excitation. The method was applied to commercially available tablets and the results were compared with those obtained by the ninhydrin method using t-and F-tests.