Abstract When recovered from ritual contexts at ancient Maya sites, obsidian blades are frequently viewed as blood-letters used for auto-sacrifice. Most evidence supporting this interpretation is circumstantial and derives from iconographic and ethnohistoric sources. Such a deductive approach does not provide a means to determine whether individual blades were used to let blood. In contrast, microscopic use-wear analysis of lithic artifacts can be used to examine blades for evidence of their use, and—provided comparative experimental data are available—to determine if they were blood-letters. The technological and use-wear analyses of 48 obsidian blades recovered from a Late Classic (c. 550–650 CE) dedicatory cache at the site of Pook's Hill, Belize, serve as a test case to explore the relationship between obsidian blades and ancient Maya auto-sacrificial blood-letting. The results of the analyses indicate that some blades from the cache may have been used to let blood; however, not all obsidian blades appear to have been used in the same way. The obsidian blood-letters recovered from the cache were used in cutting, piercing, and piercing-twisting motions. Although some blades were used to let blood, the edge and surface wear on most of the used obsidian blades are consistent with other functions, including cutting meat/skin/fresh hide, cutting or sawing wood and dry hide, cutting or sawing other soft and hard materials, and scraping hard materials. Clearly, not all blades from this ritual deposit were blood-letters, which raises questions about the manner in which such a ritual deposit was formed and the nature of ritual activity associated with caching behavior at Classic period Maya sites.