Aims: We discuss the Addicts Index (AI) and examine whether the epidemiological trends of the AI can be continued by the regional drug misuse databases (DMDs, now known as National Drug Treatment Monitoring System (NDTMS). Methods: (i) Matching individuals recorded as addicted to opiates and/or cocaine in the AI with those reported to the North Thames Drug Misuse Database (NT-DMD) 1992-1996; (ii) comparison of trends over time. Findings: Of 26,120 notifications to the AI from North Thames 73% were also reported to drug misuse database. There were no significant differences in the proportion of notifications reported over time or by sex. At least 80% of reports from specialist drug agencies were matched compared to approximately 60% of reports from GPs (X[2] p is less than 0.001). Compared to specialist drug agencies the adjusted odds ratio of being reported to NT-DMD was 0.45 (95% CI 0.40 to 0.49) for GPs. Nationally time trends in notifications to AI and reports to DMDs were highly correlated (Pearson correlation coefficients of 0.98). Conclusions: The epidemiological function of the AI can be continued. However, new strategies are urgently required to improve reporting from GPs.