A new sensitive and selective preconcentration-fluorimetric method for determination of terazosin based on its native fluorescence was developed. The analyte, initially present in aqueous matrix, was treated with an extractive non-ionic surfactant solution and separated by the clouding phenomenon. The optimum analytical conditions for terazosin assay were established. Under these conditions, linear calibration curves were obtained over the range of 1x10(-5) to 7.0 microg mL(-1) with detection and quantification limits of 1.11x10(-5) and 3.7x10(-5)microg mL(-1), respectively. Additionally, the binding constant (K(B)) for the terazosin-PONPE 7.5 system was determined given a value of 1028 L mol(-1). The developed coupled methodology, which thoroughly satisfies the typical requirements for pharmaceutical control processes, was proved to be appropriate for monitoring terazosin in actual pharmaceutical formulations and biological fluid sample. The results were validated by recovery test and by comparison with other reported methods, being highly satisfactory.