 Are you a researcher interested in finding out more about setting up your wastewater analysis program? Wastewater analysis is a rapidly developing scientific discipline that provides data on geographical and temporal trends in illicit drug use. Put your city on the map and join a network of more than 70 cities in an annual data collection. To set up wastewater-based epidemiology, there are four key steps to follow. The first step is to make contact with the national institution responsible for drug monitoring and the local authorities taking care of sewage treatment. Select those treatment plants that adequately cover the population you want to study. It is essential to know the population size that is served by the treatment plants and the total flow of wastewater pathing through the plant while you collect the samples. To obtain reliable results, samples of wastewater need to be collected before treatment starts. For a representative daily sample, approximately 100 samples should be collected within a day. These are then pulled together to a 24-hour composite. To ensure accurate measurement of drug residues, the part of the sample that will be analyzed needs to be stored in a freezer. Make sure each container is clearly labeled. Then the frozen samples are transported to a qualified laboratory. For the analysis, laboratories will deploy similar methods to those used for the detection of drugs in urine. Interpretation of wastewater data will depend on the overall objectives and shortcomings of the sample collection. Don't be surprised if the new data does not immediately match trends from other data sources on drug use. Wastewater provides extremely dynamic information. This is why trends observed here may take time to appear in other data sources. It is important to cross-check and combine your findings with other established methods to maximize the full potential of wastewater-based epidemiology. The combined results can ultimately give us a much clearer picture of drug use in Europe.