We studied the existing distribution of native Lahontan cutthroat trout Oncorhynchus clarki henshawi and exotic brook trout Salvelinus fontinalis with respect to geologic and geomorphic land-classes in the upper North Fork Humboldt River drainage, Nevada. We evaluated habitat conditions in study sites to determine which measured components of habitat structure provided the best discriminators among study stream reaches in the different land-classes and among trout-supporting and unpopulated study reaches. At a finer level of resolution, we used the habitat attributes with the most discriminatory power to plot the distributions of study areas by land-class and by presence or absence of trout along coordinate axes reflecting environmental gradients defined by these attributes.