A simple and sensitive fluorophotometric method for the determination of aldehyde was established by utilizing condensation reaction with resorcinol. In the determination of vanillin that is one of aldehydes, the calibration curve exhibited linearity over the vanillin concentration range of 3.0-7600 ng ml(-1) at an emission wavelength of 507 nm with an excitation of 410 nm and with the relative standard deviations (n=5) of 2.5%, 2.0% for 7.6 ng ml(-1), 760 ng ml(-1) of vanillin, respectively. This method was successfully applied in the assay of vanillin in cold medicine.