Bicyclesas serious meansof transportationhavegained relevance in recent years. Unfortunately,this development isaccompaniedby an increasing amount of cyclists involved in traffic accidents. Both trends are pronounced in urban areas. Traffic psychological research shows that especially anger and aggression among road users might lead to maladjusted driving and thereby to a higher accident risk. So far, research on emotions in traffic has been focusing ratheron car driversthan on cyclists.To bridge this gap and to suggest a measure assessingcyclists’ anger experience in traffic,wedeveloped a Cycling Anger Scale (CAS). On the basis ofprevious qualitative research a questionnaire was developed assessing cyclists’ anger experience in interaction with their cycling environment.N=437 cyclists completed the questionnaire. Results offactor analytical reductionsunfolded afinal23 itemsquestionnaire of the CAS (alpha reliability =.81)with four subscales: car interaction, cyclist interaction, pedestrian interaction, and traffic surveillance. The CAS correlated significantly with the Driving Anger Scalefor car drivers (DAS; r = .71) and trait anger (STAXI; r = .37) suggesting a validand complementaryinstrument for measuring cycling angerin traffic.Implications for further research and for applied issues will be discussed.