Background: To date monitoring of cryptomarkets operating on the dark net has largely focused on market size and substance availability. Less is known of country specific differences in these indicators and how they may corroborate population prevalence estimates for substance use in different countries.

Methods: All substance listings from the cryptomarket Agora were recorded over seven time points throughout February and March 2015. Agora was chosen due to its size as the second largest cryptomarket operating and the level of detail of information provided in individual substance listings. Data were collated and the number of unique sellers selling each substance by country of origin was analysed.

Results: An average of 14,456.7 substance listings were identified across sampled days from 868.7 unique sellers. The top five countries by number of listings were the USA, United Kingdom, Australia, China and the Netherlands, collectively accounting for 61.8% of all identified listings and 68% of all unique sellers. Australia was over represented in terms of sellers per capita, while China was over represented in new psychoactive substance (NPS) listings. When examined by number of listings per seller, the Netherlands and China stood out as particularly large, likely due to these countries' role in the local production of various illicit and new psychoactive substances.

Conclusions: Numbers of sellers by country of origin appear to be influenced by several factors. Australia's overrepresentation in sellers per capita may indicate its relative geographical isolation and the potential for profit margins from selling online, while China's overrepresentation in NPS listings may reflect domestic production of these substances. Continued monitoring will provide enhanced understanding of the increasingly complex and globalised nature of illicit drug markets.