Arachnid venoms present a diverse and complex matrix for investigation, with their latent potential for innovative drug and pesticide design largely unrealised. The characterisation and quantification of selected low molecular mass compounds isolated from the crude venom of the Cobalt blue tarantula (Haplopelma lividum) were the objectives of this study. Fractionation of the crude venom was performed using reversed-phase high-performance liquid chromatography, with compound identification using both electrospray ionisation ion trap mass spectrometry and quadrupole time-of-flight mass spectrometry. Four compounds were identified, and quantification on a percentage dry weight basis was achieved by liquid chromatography/electrospray ionisation tandem mass spectrometry based on the formation of their corresponding product ions. Of these the most abundant component was glutamic acid, present at a level of 0.97%. Histamine and adenosine were detected at 0.14% and 0.10% dry weight, respectively, with the polyamine spermine noted in trace amounts at 0.002%. The limits of detection and quantification were established for each of the identified components. The fragmentation profile for histamine has also been proposed. Copyright (C) 2009 John Wiley & Sons, Ltd.