This paper presents the results of the first phase of an ambitious research project aiming at modeling the changes over a 15-year period in the bus network of the city of Mississauga, Ontario, Canada, a fast-growing suburb in the greater Toronto area. Data for the Mississauga transit network, along with a host of demographic and socioeconomic variables, were analyzed. For each main route, a buffer zone representing its vicinity was constructed, and the relevant variables captured inside these zones were computed for inclusion in the proposed empirical models. Other global variables for the city were included as well to account for other effects. Results from multiple regression and simultaneous equation models attempting to relate transit supply to this group of demographic, socioeconomic, and route-specific variables are presented. Time and demand-supply interactions were taken into consideration in the simultaneous equation models. The models show that supply increases with demand and population density and decreases with number of schoolchildren in the vicinity.