This will be the Pollutant Responses in Marine Organisms (PRIMO 20) 20th annual conference which meets every other year at various locations world-wide. PRIMO 20 will be the first meeting in the U.S. since 2011, held in Long Beach, CA. This very prestigious meeting brings together top scientists and their students from around the world who investigate the impacts of chemical pollutants on marine and freshwater organisms. A major thrust historically and currently is the elucidation of underlying molecular mechanisms of toxicity. This thrust extends the relevance of the meeting from impacts in marine/aquatic environments to human health, and thus to NIEHS. PRIMO has also had particular relevance to the Superfund Research Program (SRP). The symposium will include sessions addressing mechanisms and impacts of POPs, metals, pesticides, nanomaterials, microplastics and other ubiquitous pollutants, many of which fall under the purview of the SRP. Additionally, the science emphasized includes endocrine disruption, xenobiotic metabolism, `omic approaches, genotoxicity, effects on development and transgenerational impacts, receptor-mediated signaling, and biomarkers of exposure and effect. Many Superfund Program investigators have been and continue to be highly involved in PRIMO meetings. One of PRIMO's co-founders is Dr. John Stegeman, a long-time investigator with the Boston University Superfund Research Center (see letter of support). Other SRP investigators that are regular participants in PRIMO meetings include Evan Gallagher (University of Washington), Mark Hahn (Woods Hole/Boston University), Dan Schlenk (UC Riverside), Seth Kullman (North Carolina State University), and David Hinton and Richard Di Giulio (Duke University). Several of these individuals are playing key roles in the planning for PRIMO 20. PRIMO is not affiliated with any scientific society. The meetings are funded by registration fees and modest support from a few relevant companies, government (SRP via the R13 mechanism has provided support for past meetings in the U.S.), and universities. Support beyond registration fees is used to support travel costs for graduate students.