Abstract The ancient Maya engaged in complex rituals to communicate with the supernatural world of gods and ancestors. Among the most important of these rituals was auto-sacrificial blood-letting. Blood-letting was accomplished using a variety of sharp implements, including bone awls and needles, stingray spines, thorny ropes, and obsidian blades. Our understanding of the importance of auto-sacrificial blood-letting to the Maya and the means by which it was done are primarily based on the recovery of material culture from ritually significant contexts, hieroglyphic inscriptions, iconographic representations produced in various media, and Spanish ethnohistoric documents. Based on this information, obsidian blades recovered from ceremonial or ritual contexts, like caches, burials, and caves, are usually assumed to have been blood-letters. Past interpretations of blades as blood-letters have not typically included any use-wear analysis of the blades themselves. This paper presents the results of a microscopic use-wear experiment to replicate one type of auto-sacrificial blood-letting method – piercing using obsidian lancets. In this experiment, seven obsidian lancet replicates and two flake splinter replicates were used to pierce domestic pig skin/flesh 35 times each. The use-wear that developed on the experimental tools would be helpful in identifying suspected blood-letters recovered archaeologically. Importantly, the combinations of wear features observed on the obsidian replicates differed when tools were only pushed into the pig tissue versus when they were pushed into the tissue and rotated. By combining the results of use-wear analyses like those presented in this paper with a consideration of context of recovery, the identification of obsidian blades used as blood-letters by the ancient Maya will be much more likely.