AIMS: To investigate the prevalence of awareness of the online illicit drug marketplace Silk Road (SR), consumption of drugs purchased from SR and reasons for use and non-use of SR. DESIGN AND SETTING: Global Drug Survey: purposive sample collected in late 2012. PARTICIPANTS: The base sample (n = 9470) reported recent drug purchase and resided in the United Kingdom (n = 4315, median age 24, 76% male), Australia (n = 2761, median age 32, 76% male) or the United States (n = 2394, median age 21, 80% male). MEASUREMENTS: Online questionnaire. FINDINGS: A total of 65% of US, 53% of Australian and 40% of UK respondents had heard of SR; 18% of US, 10% of UK and 7% of Australian respondents had consumed drugs purchased through SR. Across the three countries, 3,4-methylenedioxy-N-methylamphetamine (MDMA) was the most commonly purchased drug (53-60%), followed by cannabis (34-51%), lysergic acid diethylamide (LSD) (29-45%) and the 2C family (16%-27%). The most common reasons for purchasing from SR were wider range (75-89%), better quality (72-77%), greater convenience (67-69%) and the use of vendor rating systems (60-65%). The most common reasons for avoiding SR purchase were adequate drug access (63-68%) and fear of being caught (41-53%). Logistic regressions found that, compared with people from the UK, Australians [odds ratio (OR) = 3.37; 95% confidence interval (CI) = 2.29, 4.97) and Americans (OR = 1.46; 95% CI = 1.10, 1.94) were more likely to use SR due to lower prices; and to avoid SR purchase due to fear of being caught (Australia: OR = 1.65; 95% CI = 1.39, 1.96; USA: OR = 1.62; 95% CI = 1.37, 1.92). CONCLUSIONS: While reasons for Silk Road use accord with broader online commerce trends (range, quality, convenience, ratings), its appeal to drug purchasers is moderated by country-specific deterrents and market characteristics.