It was found that in buffer solution of pH 7.0, the addition of sodium dodecyl sulfate (SDS) to the solution of phenothiazine drugs, such as chlorpromazine, promethazine and trifluoperazine, showed a remarkable enhancement of their fluorescence intensity. A further study proved that the phenothiazine drugs can be determined by fluorophotometric method in micellar system. Under optimal conditions, there was a good linear relationship between fluorescence intensity and phenothiazine compounds concentration, and the detection limit of 3.0 x 10(-8) M chlorpromazine, 3.0 x 10(-8) M promethazine and 1.5 x 10(-8) M trifluoperazine (S/N=3) were also obtained. This method has been used to determine phenothiazine drugs in tablets with satisfactory results.