A survey of the leucaena toxicity status in four major goat-producing provinces of Thailand where leucaena is fed as the principal dietary component was conducted. Three adjacent dairy farms in one province where leucaena silage was being fed were also sampled. Urine samples were collected from 63 animals on six goat farms and from 32 cows on three dairy farms. Samples were acidified, cleaned and analysed by high performance liquid chromatography for 3,4-DHP and 2,3-DHP concentrations, using a modified procedure developed at the University of Queensland. Total DHP concentrations varied from 375 to 3357 µg/mL on goat farms, and from 142 to 182 µg/mL on dairy farms. These concentrations are indicative of subclinical toxicity that might cause reduced feed intake and productivity. The impact of high DHP on productivity needs to be further studied because leucaena is a readily available source of high-protein forage for ruminant industries in Thailand.