BACKGROUND The human toxicity of synthetic auxin analogue herbicides has not been extensively studied. METHODS Clinical outcome was assessed from medical records of 17 patients who had intentionally ingested auxin pesticides with active ingredients like dicamba, triclopyr, MCPA or mecoprop. The patients were interviewed after discharge to follow outcome (interval 2 to 56 months). RESULTS One patient who had ingested 500 mL of a mecoprop product died of hypotension and respiratory failure 36 hours after hospital admission. The other 16 patients recovered and were discharged by hospital day 28. After discharge, four patients died from causes not related to herbicide intoxication. In the 12 surviving patients, no long-term effects were reported. CONCLUSIONS Human toxicity of synthetic auxins appears relatively benign with conservative treatment. However, when the amount ingested is above several hundred milliliters of commercial product, especially in combination of mecoprop with other intoxicants (e.g. alcohol), shock with respiratory failure may develop and lead to death.