A flow injection analysis method for the determination of cefadroxil is proposed. The method is based on the hydrolysis of cefadroxil in sodium hydroxide solution followed by treatment with 1,4-phenylenediamine and Fe(III) in sulphuric acid solution to produce a violet color which has a maximum absorption at 600 nm. Variables such as acidity, reagent concentrations, flow rate of reagents and other FI parameters were optimized to produce the most sensitive and reproducible results. The calibration graph is linear between 80 - 320 mg/l. The detection limit is 40 mg/l with a relative standard deviation, RSD (n=6) of 1.8%. The proposed method, combining the advantages of speed and accuracy was applied to the determination of cefadroxil in pharmaceutical preparations. The results have been compared with those obtained using HPLC method (USP-procedure). Excellent agreement between the results of the proposed method and the HPLC method was observed.