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Two soil profiles were collected from undisturbed areas near the Nevada Test Site (NTS). The activity Of Cs-137 in the surface layer of the downwind Queen City Summit profile is three times higher than at the upwind site at Searchlight, NV (41.1 +/- 0.6 mBq/g vs. 13.0 +/- 10.4 mBq/g), and the Pu-239,Pu-240 activity is 100 times greater (51 +/- 2 mBq/g vs. 0.52 +/- 0.03 mBq/g). An examination of the literature suggests that the (CS)-C-137/(239,240)pu and the (239,240)pu/(239,240)pu activity ratios in soils and sediments from the northern hemisphere, due to fallout from atmospheric atomic weapons testing, have generalized values of 36 +/- 4 and 30 +/- 4, respectively (as of 1 July 1995). Deviations from these values may indicate possible contamination by sources other than fallout. Data from the surface soil of the downwind Queen City Summit profile yield a Cs-137/Pu-239,Pu-240 ratio of 0.81 +/- 0.02 and a Pu-239,Pu-240/Pu-238 ratio of 78 +/- 6. Clearly, an increase in Pu-239.240 relative to (CS)-C-137 or (238)pu can account for these observations. There is compelling evidence that this 4 excess" Pu-239.240 came from activities at the NTS during the aboveground testing of nuclear devices, more than likely from safety tests, some 40 years ago, and/or during the interim by the wind-driven resuspension of contaminated surface soil on the NTS and its transport off-site. Moreover, the two concentration profiles show that high percentages of both of these elements are retained for decades in the upper few centimeters of soil in Nevada’s desert environment. (C) 2003 Elsevier Science Ltd. All rights reserved.