BackgroundAvailability of the opioid antagonist naloxone for lay administration has grown substantially since first proposed in 1996. Gaps remain, though, in our understanding of how people who inject drugs (PWID) engage with naloxone programmes over time.AimsThis paper aimed to address three specific evidence gaps: the extent of naloxone supply to PWID; supply-source (community or prisons); and the carriage of naloxone among PWID.Materials and methodsAnalysis of Scotland?s Needle Exchange Surveillance Initiative (NESI) responses in 2011?2012 and 2013?2014 was undertaken with a specific focus on the extent of Scotland?s naloxone supply to PWID; including by source (community or prisons); and on the carriage of naloxone. Differences in responses between the two surveys were measured using Chi-square tests together with 95% confidence intervals for rate-differences over time.ResultsThe proportion of NESI participants who reported that they had been prescribed naloxone within the last year increased significantly from 8% (175/2146; 95% CI: 7?9%) in 2011?2012 to 32% (745/2331; 95% CI: 30% to 34%) in 2013?2014. In contrast, the proportion of NESI participants who carried naloxone with them on the day they were interviewed decreased significantly from 16% (27/169; 95% CI: 10% to 22%) in 2011?2012 to 5% (39/741; 95% CI: 4% to 7%) in 2013?2014.ConclusionsThe supply of naloxone to PWID has increased significantly since the introduction of a National Naloxone Programme in Scotland in January 2011. In contrast, naloxone carriage is low and decreased between the two NESI surveys; this area requires further investigation.