The European Union (EU) and the World Health Organization (WHO) have applied different approaches to facilitate the implementation of the UN Globally Harmonized System of Classification and Labelling of Chemicals (GHS). The EU applied the mandatory approach by gazetting the EU Regulation 1272/2008 incorporating GHS elements on classification, labelling and packaging of substances and mixtures in 2008; whereas the WHO utilized a voluntary approach by incorporating GHS elements in the WHO guidelines entitled 'WHO Recommended Classification of Pesticides by Hazard' in 2009. We report on an analysis of both the mandatory and voluntary approaches practised by the EU and the WHO respectively, with close reference to the GHS 'purple book'. Our findings indicate that the mandatory approach practiced by the EU covers all the GHS elements referred to in the second revised edition of the GHS 'purple book'. Hence we can conclude that the EU has implemented the GHS particularly for industrial chemicals. On the other hand, the WHO guidelines published in 2009 should be revised to address concerns raised in this paper. In addition, both mandatory and voluntary approaches should be carefully examined because the classification results may be different.