This study investigated how 191 women use period-tracking mobile applications. Findings revealed that approximately half of our respondents use some form of period-tracking mobile application. Women who use period-tracking mobile applications report using them to track and predict their menstrual cycle, keep track of menstrual symptoms, and use the information for easier and more accurate communication with their healthcare provider. In addition, women report using period-tracking mobile applications to track fertility as a means of pregnancy prevention. Women who did not use period-tracking mobile applications frequently reported that they did not feel a need to use them because their hormonal birth control predicted and regulated their period for them, and thus there was no need for a mobile application to do it. Lastly, several participants identified not using period-tracking mobile applications because they did not trust them. Reinforcing and extending previous literature, the present study highlights a tension concerning self-monitoring and self-care (Lupton, 2014), usefulness (Moglia et al., 2016), and opportunity for autonomy.