This article provides an overview of the current research on gender in human-robot interaction (HRI) including a discussion of the effects of gender characteristics in robotics design (robot gender), gender differences on interaction with robots (human gender), and some interaction effects between the two. The article also reviews research that examined the impact of the interaction between humans and robots with regard to robot appearance and behaviors, and situational factors, such as tasks and roles. Although the current state of research findings is complicated, it appears that even simple gendering of robots by manipulation of voice and name can affect humans' feelings and behaviors toward robots. These effects vary and are dependent on other factors, including human gender. Future research should focus on gender stereotypes, cultural influences, and robotic applications in various fields. At the same time, we should consider if gendering of robots, for given roles, is really necessary to encourage interactions between humans and robots.