activity strata, the 239-2405, concentrations in sieved soil aliquots can be considerably higher than obtained for ball-mill (BM) aliquots. Ratios of sieved to BM Pu activities as high as 25 are reported. For very low-level samples, however, the concentrations in BM aliquots That is, the ratio are often higher than those in sieved aliquots. of BM to sieved Pu concentrations does not appear in most cases to be constant over all activity levels. These data suggest that estimates of inventory in high-activity strata that are based only on sieved aliquots could be elevated 15 to 20 times above estimates obtained using BM fraction aliquots. Elevations on the order of 2.5 times appear possible for lower-activity strata. Pu concentrations in <100 mesh and >100 mesh soil fractions from the same soil sample are also compared. Eighteen of 21 ratios (<100 mesh/>100 mesh) were greater than 1, the highest ratio observed being 119. Regression analyses indicate the <100 mesh concentrations are significantly elevated over the >100 mesh concentrations and that the ratio is not constant over the range of activities encountered. An attempt is made to "correct" the <100 and >100 mesh Pu concentrations back to field conditions by taking into account the proportion by weight of these soil fractions in the total soil sample collected and then computing a weighted mean Pu concentration. These corrected concentrations are more nearly equal to corresponding BM concentrations from the same soil sample, but the lack of a complete correction suggests that differences between laboratories as well as differences between the actual amounts of plutonium in soil fractions may in part account for differences between BM and sieved soil results. Some possible options for future action in obtaining final estimates of 239-2405, inventory in the Tonopah Test Range (TTR) and Area 11 are discussed relative to these results. INTRODUCTION In Gilbert et aZ. (1975), the available 239-2405, and 241sm concentra- tions in soil samples from 9 of the 10 safety-shot study sites were analyzed relative to estimating the inventory and geographical distri- bution of plutonium in surface soil. 118 Data from the remaining study