The complexity of Australian funnel-web spider venoms has been explored via the combined use of MALDI-TOF mass spectrometry coupled with chromatographic separation and the analysis of venom-gland cDNA libraries. The results show that these venoms are far more complex than previously realized. We show that the venoms of Australian funnel-web spiders contain many hundreds of peptides that follow a bimodal distribution, with about 75% of the peptides having a mass of 3000-5000 Da. The mass spectral data were validated by matching the experimentally observed masses with those predicted from peptide sequences derived from analysis of venom-gland cDNA libraries. We show that multiple isoforms of these peptides are found in small chromatographic windows, which suggests that the wide distribution of close molecular weights among the chromatographic fractions probably reflects a diversity of structures and physicochemical properties. The combination of all predicted and measured parameters permits the interpretation of three-dimensional 'venom landscapes' derived from LC-MALDI analysis. We propose that these venom landscapes might have predictive value for the discovery of various groups of pharmacologically distinct toxins in complex venoms.