Assessments of the complexity of lithic technologies coming from different time periods, regions, or hominid species are recurrent features of the literature on Paleolithic archaeology. Yet the notion of lithic complexity is often defined intuitively and qualitatively, which can easily lead to circular arguments and makes difficult the comparison of assemblages across different regions and time periods. Here we propose, in the spirit of Oswalt’s techno-units, that the complexity of lithic technology can be quantified by counting the procedural units involved in tool manufacture. We define procedural units as mutually exclusive manufacturing steps that make a distinct contribution to the finished form of a technology. As a proof of concept, we use the procedural-unit approach to measure the complexity of 13 Paleolithic assemblages. While preliminary, these results provide a quantitative benchmark confirming that lithic technological complexity increased throughout the Paleolithic period. The method to meas...