The association between hygiene, sanitation, and health is well documented, yet thousands of children die each year from exposure to contaminated fecal matter. At the same time, evidence on the effectiveness of at-scale behavior change interventions to improve sanitation and hygiene practices is limited. This paper presents the results of two large-scale, government-led handwashing and sanitation promotion campaigns in rural Tanzania. For the campaign, 181 wards were randomly assigned to receive sanitation promotion, handwashing promotion, both interventions together, or neither. One year after the end of the program, sanitation wards increased latrine construction rates from 38.6 to 51 percent and reduced regular open defecation from 23.1 to 11.1 percent. Households in handwashing wards show marginal improvements in handwashing behavior related to food preparation, but not at other critical junctures. Limited interaction is observed between handwashing and sanitation on intermediate outcomes: wards that received both handwashing and sanitation promotion are less likely to have feces visible around their latrine and more likely to have a handwashing station close to their latrine facility relative to individual treatment groups. Final health effects on child health measured through diarrhea, anemia, stunting, and wasting are absent in the single-intervention groups. The combined-treatment group produces statistically detectable, but biologically insignificant and inconsistent, health impacts. The results highlight the importance of focusing on intermediate outcomes of take-up and behavior change as a critical first step in large-scale programs before realizing the changes in health that sanitation and hygiene interventions aim to deliver.