Two years into the introduction of carsharing in San Francisco, nearly 30 percent of members have gotten rid of one more cars and two-thirds stated they opted not to purchase another car. By City CarShare's second anniversary, 6.5 percent of members' trips and 10 percent of their vehicle miles traveled were in carshare vehicles. Matched-pair comparisons with a statistic control group suggest that, over time, members have reduced their total vehicular travel. Because carshare vehicles tendet to be small and fuel-efficient, per capita gasoline consumption and greenhouse gas emmissions among members also appeared to go down. Suppressed travel likely reflected a combination of influences: reduced car ownership, more judicious and selective use of cars for particular trip purpose, and carpooling among trips made using car-share vehicles. Carsharing, however, has also enhanced mobility, allowing members to conveniently reach more destinations in and around San Francisco and to do so more quickly. Because it widens mobility choices and offers a resourceful form of automobility, carsharing is a welcome addition to the urban transportation sector in cities like San Francisco.