Lack of sanitation is a huge development challenge in Kenya, but also a potentially sizeable market opportunity. The World Bank and IFCs ‘Selling Sanitation’ project worked with large plastics manufacturing firms in Nairobi to design, test, and support market development and distribution of a range of plastic latrine slabs. The products were designed from the consumer’s perspective using the Human-Centered Design approach and priced well below the cost of the prevailing concrete slab. This research brief summarizes baseline findings and monitoring results from an impact evaluation of the plastic latrine slab, evaluating its health impact and the effectiveness of niche distribution and financing mechanisms for reaching base-of-the-pyramid households. Baseline findings show that children in the study area suffer from high rates of diarrhea and many are underweight, but worm infections are rare. The majority of households at baseline had unimproved pit latrines with either no slab (49%), or a mud slab, and overall sanitation and environmental hygiene conditions are poor. Feedback on the plastic slab from monitoring visits is overwhelmingly positive, with respondents citing ease of cleaning, safety for children, and prestige. However several barriers to adoption were noted. Most participants perceive the slab as unaffordable for the target beneficiaries, while a lack of adequate follow-up and marketing from sales agents, and limited availability of the product in remote, rural villages are major obstacles to generating demand for the slab. Additional public sector resources will be needed to further support the development of distribution channels and financing mechanisms to reduce the price for base-of-the-pyramid households and increase adoption of the slab among target beneficiaries.