Terrestrial Animal Standard A large sample of beef was dried and ashed at LLNL and shipped to WOSC. The ash was spiked with a known amount of algae, blended, and reashed at 400°C. The reashed beef was blended in a small twin-cone blender, canned, and labeled. Marine Organism Standard A large fish sample was collected and ashed at LLNL and then shipped to WOSC. The ashed sample was spiked with a known amount of algae, blended, and then reashed at 400°C. The reashed sample was then blended in a small twin-cone blender, canned, and labeled. CERTIFICATION OF STANDARDS The first step in certifying the standards was to show that the methods used to prepare the samples produced a homogeneous sample. Because the vegetation standard was the first prepared, the greatest attention was given to it. Homogeneity was first tested by measuring 137 Cs in a random selection of ten aliquots of the standard by nondestructive analysis on a Ge(Li) gamma-ray spectrometer. Because the samples were not in the counting geometry normally used by WOSC, only relative activities were measured. As shown in Table 3, there was excellent agreement among the ten samples. Similarly, the 2.6% relative standard deviation of 10 measurements of radiochemically and the 4.7% relative standard deviation of 16 137 Cs done measurements of 239+240 54 (Table 4) provide evidence that the procedures used to prepare the samples produced a homogeneous sample. Because the marine and terrestrial animal standards were prepared in the same manner as the vegetation standard by adding algae and blending, their homogeneity is likewise established. In the course of this survey, the homogeneity of the vegetation and animal samples was confirmed by one of the participating laboratories (EAL). Because the soil standard had no added radioactivity, it was a slightly different case, but the 5.4% standard deviation about the mean of ten 2394240 5, analyses shows that it was likewise homogeneous (Table 5). Moreover, many analyses by the participating laboratories have further confirmed its homogeneity. Certified activities of the standards were established in two ways. First, the radioactivity of the algae used to spike samples of vegetation, fish, and beef had been measured at EML, and because it was used to prepare samples for the DOE