The characteristics of snake populations are reportedly difficult to quantify and such information exists for relatively few species, including Bullsnakes (Pituophis catenifer sayi). A Bullsnake population in southwestern Wisconsin was surveyed for three seasons (2003–05). All snakes encountered were (1) implanted with Passive Integrated Transponders for mark-recapture analyses of population size, (2) aged by size, and (3) sexed via probing and released. A subset of individuals was also implanted with radio transmitters to determine, in part, mortality rates and sources. Although recapture rates over the three years of surveying were low, an unbiased Lincoln-Petersen estimation was possible. This estimation revealed a small adult population size (N = 28.8) that was similar to the total number of adults encountered throughout the study (N = 30). Chi-squared analysis revealed that adult sex ratios were similar to 50 : 50 in all years. Mortality rates were high, particularly in females (44%), and sources of mortality were identified as predators and anthropogenic causes.