Three reliable spectrophotometric and spectrofluorimetric procedures are described for the determination of fluorouracil in bulk powder and ampoules in the presence of its degradation products. One spectrophotometric procedure, based on measurement at 555 nm of the violet-coloured complex formed by fluorouracil with cobalt(II), has a detection limit of 0.03 mg mL(-1). Two sensitive spectrofluorimetric procedures are also proposed. One is based on measurement of the intrinsic fluorescence of the liberated fluorouracil at 375 nm, after precipitation as its cobalt(II) complex, decomposition of the precipitate with sulphuric acid and excitation at 295 nm. The second depends on excitation of the fluorouracil-cobalt(II) complex at 395 nm and measuring its fluorescence at 483 nm. The limits of detection of the two spectrofluorimetric procedures are 0.5 and 2 microg mL(-1), respectively. The three procedures have been used successfully for the determination of fluorouracil ampoules. The validity of the methods has been assessed by applying the standard addition technique.