Abstract: The oxidation of the alkaloid brucine by chromium(VI) in sulfuric acid medium in the presence and absence of oxalic acid is described. Photometric monitoring of a red intermediate (λmax = 525 nm) permits determinations of both chromium (VI) and brucine at low concentrations (Cr(VI), 0-7.5 µg mL-1; brucine, 0-197 µg mL-1) in an unsegmented continuous-flow system by direct injection of the sample into the detection area. Detection limits are 0.1 µg mL-1 for chromium and 4 µg mL-1 for brucine. Other alkaloids structurally related to brucine (e.g., strychnine, yohimbine and corynanthine) do not give intermediates with the high molar absorptivity exhibited by brucine. Determination of chromium in water samples and standards is described.