The process of examination marking is complex, requiring examiners to engage in a variety of cognitive operations. While consideration has been given to marking practices in a few specific contexts, those of General Certificate of Secondary Education (GCSE) examiners have yet to receive serious attention. This study's aims, therefore, were: first, to investigate the cognitive strategies used when marking GCSEs; and second, to interpret them within the context of psychological theories of human judgement. Two contrasting GCSE examination papers were considered: Mathematics used a "points-based" marking scheme, while Business Studies relied on a "levels-based" scheme. Small groups of experienced examiners marked script samples, and using a concurrent "think aloud" method, verbal protocols were obtained. Using a semi-structured interview schedule, the examiners were then questioned retrospectively. Qualitative data analysis supported a model of five distinct cognitive marking strategies, which can be interpreted within dual-processing theories of judgement. The implications for GCSE marking are discussed. (Contains 1 table.)