actively involved in the statistical design and analysis aspects of these studies and takes the opportunity here to review some of these methods and to suggest some new approaches that might be useful in future work. This review may be particularly helpful at this time since new studies at nuclear test sites at NTS are expected to begin soon, as are experimental plots to evaluate the feasibility of several alternative clean-up treatments in desert environments. Some of the general planning aspects of these new studies are also discussed. SAMPLING FOR INVENTORY AND GEOGRAPHICAL DISTRIBUTION OF Pu Review and Possible New Approaches The FIDLER (Field Instrument for the Determination of Low-Energy Radiation) has been successfully used as a survey instrument at most safety-shot sites to delineate the approximate distribution of 241an in surface soil. The only exception is A site in Area 11, where the FIDLER could not be used since the principal contaminant is 235y, (At this site, soil samples were collected on a grid system and 235 U on the Ge(Li) system.) FIDLER survey readings give analyzed for a general notion of the geographical distribution of 2414 contamination in surface soil and are useful for defining strata for estimating plutonium inventory in soil. Strata maps drawn from these FIDLER survey data are given in Figs. 4 through 14 in Gilbert et al. (1975). While a major advantage of the FIDLER instrument is the relative ease and speed at which a study site can be surveyed, it has been our experience that two surveys of an area are usually required to obtain the necessary detail in distribution desired for establishing strata: sal, an initial survey to learn the general pattern of disper- followed by a second survey on a finer grid to obtain greater detail. The only comment here is that greater use of any prior survey information that may exist on the dispersal of contaminants could reduce the time necessary to obtain the more detailed survey information needed for current studies. 102