Technical Abstract: Standard Reference material (SRM) 1849 is intended primarily for validation of methods for determining proximates, fatty acids, vitamins, elements and nucleotides in infant and adult nutritional formulas and similar materials. This SRM can also be used for quality assurance when assigning values to in-house reference materials. The SRM is a milk-based hybrid infant/adult nutritional powder, prepared by a manufacturer of infant formula and adult nutritional products. A base liquid containing all constituents was conventionally heat processed, homogenized and then spray-dried. The material is a hybrid and not an infant formula. A unit of SRM 1849 consists of 10 packets each containing approximately 10 g of material. Certified concentrations for selected fatty acids, vitamins and elements are provided in the Certificate of analysis. Analyses for value assignment were performed by NIST, the U.S. Department of Agriculture and collaborating laboratories. Certified values are calculated as the mean of mean values from NIST methods, mean of data provided by USDA, the median of results from collaborating laboratories and the mean provided by the manufacturer.