There are two facets to the problem in South Asia, both of which are unacceptable. The first is a problem of scale: 716 million men, women, and children defecate in the open every day in South Asia, especially in rural areas: a veritable sanitation crisis that impairs progress in the region. Many districts in India, Nepal, and Pakistan fall in this category. The second, and in many ways more pernicious problem, particularly in South Asia, is one of exclusion, where different categories of people are not able to access and use safe sanitation facilities. These categories of people include those who are socially and economically marginalized or excluded, and those who cannot use standard designs. This catalytic working paper, including a bibliography, was developed for the Technical Session during the 4th South Asian Conference on Sanitation (SACOSAN IV) Reaching the Unserved: Equity and Inclusion in South Asia. It is intended for discussion leading to collaborative action.