Recebido em 6/8/08; aceito em 19/1/09; publicado na web em 3/7/09 This paper reports an analytical method for the determination of ambroxol in micellar medium by spot test-diffuse reflectance spectroscopy. The reflectance measurements were performed analyzing the colored compound (λ= 520 nm) produced from the reaction between ambroxol and p-dimethylaminocinnamaldehyde on the surface filter paper. The linear range was from 1.21 × 10 −3 to 9.65 × 10 −3 mol L -1 (500 -4000 µg mL -1). The limit of detection and quantification were 3.50 x 10 -4 mol L -1 (145 µg mL -1 ) and 1.16 x 10 -3 mol L -1 (481 µg mL -1 ), respectively. Five commercial samples were analysed and the results obtained by the proposed method were in good agreement with those obtained by the literature method at 95% confidence level.