In Iran, road traffic injuries are the first cause of burden of disease and motorcyclists are the most vulnerable road users. Elliot and colleagues developed the "Motorcycle Rider Behavior Questionnaire" (MRBQ), on the basis of Reason's "Driver Behavior Questionnaire" (DBQ) in 2007. The purpose of this study was to assess the validity and reliability of a Persian version of MRBQ. The 43-item MRBQ was adapted to Persian according to translation-back translation method. The questionnaire was significantly revised after assessment of content validity. In the revised version, 10 items of original MRBQ were deleted and 15 new items were added. The revised MRBQ was used in a survey of 518 motorcyclists. To assess the construct validity of MRBQ, we used Buss-Perry Aggression questionnaire concurrently on all of the subjects. After three weeks, we carried out the retest study on 119 out of 518 subjects. The mean age of the subjects was 32.5 years (SD=8.8). All of the participants were male with mean of 9.3 years of motorcycle riding experience (SD=7.3). Principal Components Analysis (PCA) showed six subscales: "Speed Violations", "Traffic Errors", "Safety Violations", "Traffic Violations", "Stunts" and "Control Errors", which accounted for 36.44% of total variance together. For each of these subscales, Cronbach's Alpha was between 0.79 to 0.91. Intraclass Correlation Coefficient for six subscales and total questionnaire were from 0.73 to 0.91. There were significant correlations between MRBQ subscales and subscales of Buss-Perry aggression questionnaire. The results indicated that the 48-item Persian version of MRBQ is a suitable measure for studying motorcyclists' behavior.