This freeze-dried mussel tissue standard reference material (SRM) is intended for use in evaluating analytical methods for the determination of selected polycyclic aromatic hydrocarbons (PAHs), polychlorinated biphenyl (PCB) congeners, chlorinated pesticides, polybrominated diphenyl ether (PBDE) congeners, hexabromocyclododecane (HBCD) isomers, methylmercury, inorganic mercury, and total mercury in marine bivalve mollusk tissue and similar matrices.