A simple and very sensitive method for the spectrophotometric determination of manganese in pharmacological preparations and vegetable fertilizers is proposed. The method is based on the formation of a blue coloured complex of Mn (II) with 9-phenyl-2,3,7-trihydroxy-6-fluorone (PF) in the presence of cetylpyridinium chloride (CP) and Triton X-100. Optimum concentrations of PF, CP, Triton X-100 and pH ensuring maximum absorbance were defined. The complex Mn(II)-PF-CP-Triton X-100 shows maximum absorbance at 591nm with the molar absorptivity value 1.77105Lmol1cm1. The detection limit of the method is 0.004gmL1. The Beers law is obeyed for manganese concentrations in the range 0.020.2gmL1. The effect of foreign ions was elucidated. The statistical evaluation of the method was carried out for six determination using 5g Mn and the following results were obtained: standard deviation 0.021, confidence interval 5.050.05g Mn. The method has been applied for the determination of manganese in pharmacological preparations (Biovital, Kinder Biovital) and vegetable fertilizers (Hydrovit 100, Florovit).