A selective and highly sensitive fluorometric method was developed for the determination of four alpha-aminocephalosporins, namely cefaclor, cefadroxil, cephalexin and cephradine. The method involves the reaction of the target compounds with fluorescamine at a specific pH, ranging from 7.8 to 8.4. The produced derivatives exhibit maximum fluorescence intensities at 472-478 nm after excitation at 370-372 nm. The method is highly specific because other alpha-aminocephalosporins whose alpha amino group was blocked do not react similarly and hence do not interfere. At the specific pH range of the reaction where no degradation may occur with that medium the proposed method can be utilised as a stability-indicating assay. The different experimental parameters affecting the derivatisation reaction were carefully studied and incorporated into the procedure. Under the described conditions, the proposed method is linear over the concentration range of 0.05(-1) microg/ml(-1) for both cefaclor and cephalexin, and 0.05-0.65 and 0.025-0.5 microg/ml(-1) for cefadroxil and cepharadine, respectively and the coefficients of determination were greater than 0.999 (n = 3). The recoveries of the title compounds from spiked serum ranged from 88.6 to 89.7% and from spiked urine from 92.2 to 93.3% with a limit of quantitation (LOQ) of 25-50 ng/ml(-1) and limit of detection (LOD) of 5 ng/ml(-1) (S/N = 2) for all drugs. The mechanism of the fluorometric reaction is proposed and the advantages of the proposed method are discussed.