Identification of a case of acute salicylate intoxication using 300 MHz 1H NMR spectroscopy of a urine sample is reported. It has been achieved by using a combination of a one-dimensional experiment with water presaturation and a two-dimensional homonuclear J-resolved experiment. By these means, lysine and the three major metabolites of acetylsalicylic acid have been assigned in the crude urine. The results are compared with those obtained at 600 MHz and with classical biochemical methods. The use of this method for routine diagnosis in biological analysis is discussed.