Gender plays a key role in the process of language variation. Men and women use language in different ways, according to the expected behavior patterns associated with their status in the communities. In this paper, we present a first description of gender distinctions in the usage of Twitter hashtags. After analyzing data collected from more than 650,000 tagged tweets concerning three different subjects, we concluded that gender can be considered a social factor that influences the user's choice of particular hashtags about a given topic. This study aims to increase knowledge about human behavior in free tagging environments and may be useful to the development of tag recommendation systems based on users' collective preferences.