This study investigated the behavioural, attitudinal and traffic factors contributing to red light infringement by Australian cyclists using a national online survey. The survey was conducted from February to May 2010. In total, 2061 cyclists completed the survey and 37.3% reported that they had ridden through a signalised intersection during the red light phase. The main predictive characteristics for infringement were: gender with males more likely to offend than females (OR: 1.54, CI: 1.22–1.94); age with older cyclists less likely to infringe compared to younger cyclists 18–29 years (30–49 yrs: OR: 0.71, CI: 0.52–0.96; 50+ yrs: OR: 0.51, CI: 0.35–0.74), and; crash involvement with cyclists more likely to infringe at red lights if they had not previously been involved in a bicycle–vehicle crash while riding (OR: 1.35; CI: 1.10–1.65). The main reasons given for red light infringement were: to turn left (32.0%); because the inductive loop detector did not detect their bike (24.2%); when there was no other road users present (16.6%); at a pedestrian crossing (10.7%); and ‘Other’ (16.5%). A multinomial logistic regression model was constructed to examine the associations between cyclist characteristics and reasons for infringement. Findings suggest that some cyclists are motivated to infringe by their perception that their behaviour is safe and that infrastructure factors were associated with infringement. Ways to manage this, potentially risky, behaviour including behaviour programmes, more cyclist-inclusive infrastructure and enforcement are discussed.