A RP-HPLC method for detecting and quantifying beta-N-oxalyl-L-alpha,beta-diaminopropanoic acid (beta-ODAP) the neurotoxin in grasspea (Lathyrus sativus) seeds by pre-column derivatization was developed. Seed extracts of grasspea were derivatized with o-phthalaldehyde in the presence of beta-mercaptoethanol and subjected to RP-HPLC on a C-18 column (2501 x 4.6 i.d. mm). The derivatized beta-ODAP could be detected either by UV at 340 nm or by fluorescence. The relatively instantaneous derivatization procedure and high sensitivity make this method useful for detection of the less expensive and drought tolerant grasspea seeds a common adulterant in edible legume seeds such as chickpea (Cicer arietinum) and redgram (Cajanus cajan). The sensitivity of this method for the detection of beta-ODAP in legume seed flour was 3.5 0.1ppm. The accuracy, precision, linearity and limit of detection were consistent with that previously reported in literature. This method can be potentially applied for the detection of the neurotoxin in low-toxin varieties of the grasspea seeds being developed and those reported in other plants. All rights reserved, Elsevier.