For the latest release of i2b2 (version 1.8.0) we made significant redesign and implementation changes to the user interface (the i2b2 “web client”).To demonstrate the new web client plugin architecture, we created a new plugin that uses area-proportional Venn diagrams to display the overlap of several previously saved patient cohorts (i2b2 “patient sets”). One example of how this visualization can be used is to quickly identify the intersection sizes of three patient populations: patients with autism, patients with gastrointestinal disorders, and patients without food allergies. First, the three groups are saved as separate patient sets. The user then drags and drops the patient sets onto the visualization plugin loaded on the right side of the application (Figure 1). Another use case is optimizing clinical trial design. By visualizing the overlap between inclusion and exclusion criteria, the user can see where to make adjustments to increase the number of patients eligible for the trial.Open-source code for the plugin can be accessed from Neomancy at https://github.com/Neomancy/i2b2-venn-plugin