The influence of urbanization on hydrology, habitat, and aquatic communities has received increased attention by stream ecologists over the last decade. However, few studies have been conducted in semi-arid areas. To address this issue, invertebrate, fish, hydrology, habitat, water-chemistry, and land-use data were collected annually from 13 sites in the Fountain Creek basin, Colorado, from 2003 - 2005. Relations between stream hydrology (high-flow magnitude, high-flow frequency, and stream flashiness), water chemistry (dissolved nitrate plus nitrite), and habitat (percent pool, lower bank capacity, and maximum bank height) to urbanization (impervious surface) were evident (Spearman’s rho >0.60, range 0.63-0.81). An exploratory multivariate technique identified various subsets of environmental variables that described patterns in invertebrate community structure. The strongest subset (rho = 0.71) included high-flow frequency, lower bank capacity, and nitrite plus nitrate concentration. Relations between fish community structure were much weaker (rho = 0.25). Results of this study are not substantiated by other regional studies where relations between urbanization, habitat, water chemistry, hydrology, and biology were not evident. A conceptual model was developed to help design additional studies on how biological communities are influenced by urbanization in similar streams along the Front Range of Colorado.