Upon on-line photochemical reaction carbamazepine (CBZ) can be converted to a strong fluorescent compound which has a maximum emission wavelength of 478 nm and maximum excitation wavelength of 254 nm. Acidity of reaction medium and the acid type were found to be critical for the on-line photochemically induced fluorescence, dilute hydrochloric acid being the most suitable. Based on these observations, a flow injection photochemical spectrofluorimetric approach for determination of the drug was developed. At optimized conditions, a detection limit of 0.08 ng x ml(-1) CBZ was achieved at the sampling rate of 80 h(-1). Eleven determinations of a 100 ng ml(-1) CBZ standard solution gave a RSD of 0.45%. A linear calibration curve was obtained in the CBZ concentration range of 2-250 ng x ml(-1). The developed method was successfully applied to assay the CBZ contents in pharmaceutical tablets.