ABSTRACT: Marine mussels (Mytilus spp.) were sampled by Washington Department of Fish and Wildlife staff and citizen science volunteers at 23 national Mussel Watch (MW) program sites during the winter season (December through March) of 2011/12. These mussels were collected in order to avoid a break in the regular, biennial sampling for MW, which has produced a 25-year toxic contaminant time trend series for nearshore biota in Washington State. Staff and volunteers sampled mussels at 90% of the MW sites listed in a Mussel Watch - Phase 1 Quality Assurance Project Plan (QAPP) developed for this study and only two sites were dropped due to a lack of mussels. In addition, volunteers from the Snohomish County Marine Resources Committee and the Stillaguamish Tribe collected mussels at five sites in Snohomish County not originally listed on the QAPP. After collection all the mussels were sent to contracted analytical laboratories with the agreement that the MW program would finance immediate analyses of mussels from a subset of stations prioritized by WDFW staff, and archive the remaining samples for later analysis.