To determine the association of built-environment, social-environment, and personal-level factors with bicycling for transportation, among adult city dwellers. Survey of a representative sample of 1000 inhabitants of the city of Graz, Austria, using a computer-assisted telephone interview addressing cycling behavior and associated personal, social and environmental factors. The prevalence of biking for transportation was 22.5%. After adjustment for gender, age, education, physical activity level and distance from home to destination, cycling was positively associated with the presence of bike lane connectivity (OR=2.09) and social support/modeling (OR=1.62), and negatively associated with the perceived barriers of "physical discomfort" (OR=0.49) and "an impractical transport mode" (OR=0.50). Analysis of interactions indicated that the effect of the perceived benefit of "rapidity" was stronger in physically active persons than inactive individuals, and the effect of the perceived barrier of "an impractical mode of transportation" was stronger among women than men. In addition to cycling-related social support and perceived benefits and barriers, bike lane connectivity may be an important determinant of cycling as a means of transportation among adult city dwellers.