What is the place for critical ethnography in global health and other related forms of international intervention? This essay explores this question through my experience collaborating with a nongovernmental organization (NGO) working to improve children’s well-being in El Salvador and with a team of quantitatively oriented researchers evaluating the NGO’s project. I adopt as an analytic lens one of the metrics the researchers used – the Battelle Developmental Inventory – in order to explore the possibilities for dialogue among quantitative and qualitative methods (and researchers). At issue is the place that critique can have in such dialogues, particularly when the aims of NGOs, public health researchers, and ethnographers can sometimes be at odds. Ultimately, I make the case that viewing critique as a praxis, keeping an eye on the commensurability of aims, and being prepared for occasional productive friction are some practical steps for bringing critical ethnographic perspectives into contact with interventions.