This study examined the relationship between dysmenorrhea and insomnia, as well as variability in sleep across the menstrual cycle. Participants were 89 women, ages 18 to 24 (M = 18.63, SD = 0.93), who completed daily surveys for five weeks. On the second day of menses, they completed a questionnaire regarding dysmenorrhea. Participants having insomnia rated their dysmenorrhea as being more severe and causing more interference with daily activities than did participants without insomnia. Insomnia severity was directly associated with dysmenorrhea severity and interference. Sleep onset latency was longer and sleep efficiency was lower in participants with severe dysmenorrhea than in those with mild dysmenorrhea. Further, participants with mild dysmenorrhea reported significantly better sleep quality than did those having moderate or severe dysmenorrhea. Additionally, wake time after sleep onset was shortest and number of awakenings was lowest around the time of ovulation. Future research should examine whether treating dysmenorrhea or insomnia alone results in improvements in the other condition.