I checked environmental reasons on your poll, but it's really a combination of factors for me -- the exercise, conserving gas, and the environment. To be honest, though, probably the biggest reason why I bike commute is simply because I like to ride. Saving money is probably the lowest priority for me because I spend enough on bike gear (clothes, parts, tires, etc.) to offset any savings from not buying gas. Bike commuting does help me justify some of my bike expenditures, however, which is good.