Women with adequatemenstrual hygiene have access to soap and water for washing, access to clean sanitarymaterials (that can be changed in private), and access to a place for the hygienic disposal of used sanitary materials or washing reusable pads. Inadequate menstrual hygiene is common among women in low-resource countries. In recent years, menstrual hygiene has recently received increased global attention as a public health and human rights issue. Women with inadequate menstrual hygiene are at risk of infections and poor health-related quality of life. There is increasing evidence of interventions that improve knowledge and practices of menstrual hygiene in women. Few studies have addressed the extent to which menstrual hygiene is an issue for low-income women in the United States. The aim of this study was to assess the menstrual hygiene needs of low-income women in St Louis, Mo. A needs assessment was conducted using an exploratory, cross-sectional design to examine the menstrual hygiene needs of a population of approximately 31,000 low-income women 18 years or older living in poverty in 2017, who were served by not-for-profit community organizations. Women were recruited from a purposive sample of 10 not-for-profit community organizations serving low-income women in St Louis. Between July 2017 and March 2018, interviewer-administered surveys were conducted in 184 women; 3 focus group discussions involving 17 women were also conducted. The data obtained from the surveys and focus groups showed where and how the participants accessed menstrual hygiene products and how they coped when they cannot afford to buy them. An electronic survey of 18 community service organizations was conducted using a snowball sampling strategy to assess what services and supplies they provide for menstrual hygiene. All women asked to participate in the interviews and the focus groups did so. Nearly two-thirds (64%) of women at some point during the previous year were unable to afford needed menstrual hygiene supplies; this occurred monthly in 21% of the participants. To manage their menses, many women had used strips of cloth, rags, tissues, or toilet paper, and several reported using their children's diapers, adult incontinence diapers, or paper towels taken from public restrooms. Nearly half of women surveyed (46%) could not afford to buy both menstrual hygiene products and food over the previous 12 months. Women reported no difference in menstrual hygiene needs by age. Although 90% of women usually purchased their own menstrual hygiene products, nearly two-thirds relied on donations from community service organizations at some point. Among 18 organizations that completed the electronic survey, 13 provide menstrual hygiene supplies to their clients, and only 2 provide menstrual hygiene education. Important barriers to menstrual hygiene include money to purchase supplies, transportation to reach stores where bulk quantities can be purchased more cheaply, and safety and security access to toilet facilities. The data show that many low-income women in this urban population lack menstrual hygiene supplies but cannot afford to buy them. Although not-for-profit community organizations that serve low-income women often help them obtain menstrual hygiene products, this assistance is not consistent. Access to menstrual hygiene products is a basic necessity for all women and should be regarded as a basic women's right. Failure to meet these basic biological needs in the United States is an affront to women's dignity, and the issue must be addressed. Women's health care providers and their professional organizations are encouraged to advocate for change.