This secondary data source is a quick and inexpensive methodology that lends itself to supplementing more costly primary data analyses. The focus of this guide is on underreported illicit drugs, emphasizing powder and crack cocaine, heroin and methamphetamine. It makes good economic sense to try and prevent substance abuse. In 1997, the price tag for substance abuse was $11.9 billion; all costs attributed to substance abuse totaled $294 billion. Using multiple data sources is critical to the success of MIA analysis. Combining hospital emergency room data with human services and criminal justice system data provides a rich picture of issues, trends and possible places in these systems where effective interventions can be created. In addition, by analyzing the same types of data over different time periods, trends emerge. As one might expect, drug use shifts as market demands and price changes as well as new drug forms, i.e., the move from powder cocaine to crack cocaine in the 1980s. When analyzing multiple data sources, it would be prudent to use a unique personal identifier (possibly a social security number) to avoid duplication. Descriptive statistics (frequencies, percentages and averages) tend to be the form of data sought when using MIA. The reporting of the findings, as interventions, are tailored to the audience. A more detailed report with descriptions of the methodology and data sources would be of interest to researchers, whereas planners and policymakers would welcome a short summary report. Sharing the findings and recommendations with the agencies whose data was analyzed would be extremely valuable and increase collaboration among the researchers, policymakers and other key stakeholders grappling with this public health issue. Lastly, easy-to-understand graphics are useful for all audiences. Tables, appendices