The aim of this study was to investigate the relationship between the stringency of NOx regulation and environmental technological change in the EU and US glass industry. A time series of patents on NOx primary reduction measures, including oxy-fuel technology drawn from the international patent class ‘glass melting furnaces’, serves as an indicator of technological change. A qualitative analysis based on patent data and face-to-face interviews with glass industry representatives revealed that NOx-related patent registrations, particularly in Germany and the US, are closely associated with early national NOx regulations and to a more limited extent with international regulation. Quantitative analysis of patent citations as a measure of knowledge spillover between patents showed that the strong environmental knowledge of Germany and the US is not only widely used within these countries, and also in other countries where environmental regulation began at a later stage. Copyright © 2013 John Wiley & Sons, Ltd and ERP Environment.