A routine procedure in which the Technicon Auto Analyzer is used for the determination of boron in plant tissue with azomethine H is described. The preparation of the reagent as the condensation product of H-acid and salicylaldehyde is given. The reagent is highly sensitive to boron, and only copper, iron and aluminium interfere. These interference effects are eliminated with an EDTA solution. The procedure is performed in aqueous medium thus simplifying its adaptation to an automated system and its use for routine determination.