The likelihood of doing risky behavior such as drug use, high-risk sexual behavior, and adjustment problems in youth period is high. The present study aimed to investigate the prevalence of risky behaviors among first-year medical students. Objectives: In this research, we intend to study the extent of risk behaviors based on demographic variables among medical students of Hamadan. Materials and Methods: This cross-sectional study was carried out on all first-year medical students (498 females and 292 males) of Hamadan University of Medical Sciences in the academic year 2016-2017. The study data were collected by the Iranian Youth Risk-Taking Scale (IYRTS). Results: The mean scores of risky driving (2.86) (53.60%) and sexual relationship/attitude (2.43) (48.60%) were higher than other high-risk behaviors while the mean scores of drug use (1.33) (26.60%) and drinking (1.57) (31.40%) were lower than other risky behaviors in medical students. Results of the Chi-square test indicated that the risky behaviors in males were significantly higher than those in females (P<0.05). The results of 1-sample t-test indicated that the prevalence of risky driving, violence, smoking, drug use and drinking in Hamadan medical students is less than average, and the sexual relationship and attitude among these students is at moderate level (P>0.05). The relationship between age and education with risky driving was negative and statistically significant. The violence was positively related to drinking and smoking. The sexual relation, attitude, and drinking statically significant. Conclusion: Since some sorts of risky behaviors among students are prevalent, it seems logical to inform adolescents and youth about such high-risk behaviors and related health issues.