Concerns about bicycle-related deaths and injuries have led to extensive injury prevention efforts in the United States, yet these concerns are not universal. For instance, in France attitudes toward bicycle safety are quite different. To understand more about variation in urban bicycle safety behavior, we observed passing bicyclists in Paris and Boston. In addition to helmet use, we looked at use of lights at night. Among 5,808 passing bicyclists, there were large differences in helmet and light use: only 2.2% of Paris bicyclists wore helmets compared to 31.5% in Boston. In contrast, 46.8% of nighttime Paris bicyclists had working head or tail lights compared to only 14.8% in Boston. These large and seemingly contradictory percentages are the result of different laws and public health priorities, types of bicycle riding, and perceived risks. Suggestions for further research and practical ways to improve U.S. bicycle safety behavior are discussed.