NIST releases Certification of Standard Reference Material (SRM) 968f: Fat-Soluble Vitamins in Frozen Human Serum (NIST SP 260-188). This publication is intended for use in validating methods for determining fat-soluble vitamins in human serum and plasma and qualifying control materials produced in-house and analyzed using those methods. It is the seventh member of the SRM 968 series of certified reference materials. These materials were developed to help address the clinical, epidemiological, and nutritional communities’ need for well-characterized reference materials.