Trapping data indicate that resident rodent species and most rodent populations were fewer in number in the higher Pu activity strata in Area 11-C. Therefore, collections of adequate samples of resident rodents from the vicinity of GZ will require extended collecting effort encompassing several reproductive seasons. Preliminary results of hematologic studies of rodents in Area 11-C indicate that there is a correlation between Pu body burdens and depressions in some leukocyte counts. Regression analysis revealed a significant (P<.01) reduction in relative number of lymphocytes, with an increase in Pu carcass burdens of Dtpodomys mierops and Perognathus longimembris. Leukocyte counts were signifi- cantly lower (P<.01) with an increased Pu carcass burden in D, merriamt. More data from animals with high Pu tissue burdens are needed before effects of Pu on the hemopoietic system of rodents can be properly evaluated. INTRODUCTION Plutonium (Pu) is an important environmental factor in certain areas of Nevada Test Site (NTS) and Tonopah Test Range (TTR). The Nevada Applied Ecology Group (NAEG) has been engaged in studies related to distribution of Pu in these areas in order to evaluate effects of Pu on native plants, animals, and ecosystems and their possible relationships to man. Ecological studies of vertebrates in three Pu-contaminated areas of NTS began in Spring, 1972, and were expanded to include four areas of TTR in Fall, 1973. During the initial phases of these studies, emphasis was on the modification of standardized procedures for qualitative and quantitative inventories of small vertebrate populations. Additional techniques for the collection and preparation of vertebrate samples for radioanalysis were developed and improved. These methods and much of the basic inventory and ecological data for small vertebrates have been previously reported (Moor and Bradley, 1974; Bradley and Moor, 1975). Emphasis has changed since the last formal report (Bradley and Moor, 1975) with the completion of initial species inventories of NTS and TTR. Dominant vertebrate species of various trophic levels have now been identified in NAEG Study Areas, and much is known about their numbers and seasonal population dynamics. Efforts are now being directed at evaluating uptake of Pu and Am in different trophic levels in relation to radioisotope concentrations within the general activity range of individual animals. Initial attempts to evaluate some possible irradiation effects have recently been undertaken with initiation of hematological studies of lizards and rodents resident in NAEG Intensive Study Areas. This report consists primarily of presentation and analysis of radioanalytical data on rodents and lizards of some NAEG Study Areas of NTS and TTR. In addition, methodology and some preliminary results of initial hematological Studies of rodents are presented. 194