A rapid photometric method is proposed for determining boron in natural waters, based on the separation of boron from interfering impurities by extraction from weakly acidic solutions with a mixture of 2,6-dimethyloctanediol-3,6 and n-amyl or iso-amyl alcohol (1:4) and determination in the reextract at pH 5 in the form of compounds with H-resorcin and uranine. The lower limit of the determined quantities of boron is 0. 05 g/ml.