Conservation Measure 22-07 (2008) requires vessels fishing in the Ross Sea (and most areas south of 60°S) to collect and monitor longline bycatch for VME taxa, and implement a move-on rule if required. To ensure effective monitoring, an evaluation of VME taxa classification by Scientific Observers from four vessels in the Ross Sea Antarctic toothfish longline fishery during the 2009-10 season was conducted. Scientific Observers classified invertebrate bycatch using a revised and expanded VME taxa classification guide, and retained 1109 samples from 1272 longline segments for subsequent classification by parataxonomists and/or taxonomists, from which 4555 specimens were identified. Improvements made to the classification guide, along with specific training, benefitted the accuracy of data collection. Comparison of the observer’s classification versus the taxonomist’s classification showed that for most groups, the observer classifications were reasonably precise (88% accuracy). Some problems in distinguishing demosponges and hexactinellid sponges, sponges from ascidians, and stylasterid hydrocorals from gorgonian corals remains. Scientific Observers rarely classified non-VME taxa as VME taxa (23 of 1008 samples). In the Echinodermata group, brittle stars (a non-VME taxon) were sometimes recorded as snake stars (a VME taxon). Briefings prior to sailing and additional training materials can address most remaining issues.