Recently, bites by the colubrid Boiga irregularis (brown tree snake) in infants and young children on Guam have produced severe systemic reactions which bear some resemblance to classical manifestations of neurotoxic venom poisoning. This study demonstrates that the Duvernoy's secretion which elicits these reactions is a remarkably simple venom secretion with comparatively low toxicity and generally weak enzymatic activity. The intravenous LD50 for Swiss-Webster mice was approximately 80 mg/kg; significant neurotoxic manifestations were not observed in mouse trials. Deaths of lethally challenged mice occurred within minutes of injection, and appeared to result from cardiopulmonary crises. Duvernoy's secretion yields, protein content, enzyme activities, electrophoretic data and toxicity characteristics of the secretion are presented.