Flow injection (FI) spectrophotometric sequential determination of Cr(VI) and Cr(III) has been proposed by using flow systems assembled with inexpensive and easily available components. It is based on the reaction of Cr(VI) with 1,5-dipenylcarbazide(DPC) to form a colored complex for the determination of Cr(VI). Cr(III) is oxidized in-line to Cr(VI) by Ce(IV) yielding the total Cr concentration. From the difference, Cr(III) concentration can be evaluated. Solid phase extraction with C 18 in-valve mini-column provides on-line preseparation and preconcentration. Single standard calibration is possible. Optimization for the conditions was investigated. The FI procedure developed has been applied for speciation of Cr(VI) and Cr(III) in waste water samples taken from industry in Thailand. The results obtained agree well with those obtained by ICP-AES.