Spectrofluorometric method for determination of promethazine hydrochloride, thioridazine hydrochloride and perazine dimaleate in the pure form and in drugs is described. Fluorescence excitation spectra of series of aqueous solutions were measured. The fluorescence signal was found to be a linear function of the promethazine hydrochloride (PTM) concentration in the range: 0.30-20.02 ppm, thioridazine hydrochloride (TR): (0.43-21.70 ppm and perazine dimaleate (PDM): 0.85-50.60 ppm. The excitation spectra were used for determination of phenothiazine derivatives in pharmaceutical formulations such as: Diphergan, Thioridazin and Pernazinum. The influence of K+, Na+, Mg2+ i Ca2+ cations on the fluorescence intensity of phenothiazine derivatives was also studied.