This Measurement Good Practice Guide covers real-time, on-line cure monitoring in the industrial processing of thermosetting polymer-based materials, such as fibre-reinforced composites, adhesives and coatings. The Guide focuses on the five most commercially well-developed cure monitoring techniques: thermal, ultrasonic, acoustic, dielectric and strain sensing. The procedure, theory and analysis for each measurement technique is described in detail and their respective sensitivities to important stages during cure processing discussed. Typical examples of obtainable results are demonstrated using laboratory investigations, with supporting evidence of their application to real environments, processes and problems being provided by three industrial case studies. Recommendations are made on the choice of technique and important considerations when making an appropriate selection. Finally, the overall benefits of adopting cure monitoring are highlighted. The Guide provides a consolidated source of information to help exploit cure-monitoring technology.