The question of whether marking speed is related to marking accuracy is important for training examiners and planning realistic marking schedules. We explored marking speed in the context of a past examination for an international biology qualification for 14- to 16-year-olds. Forty-two markers with differing backgrounds experimentally marked 23 diverse examination questions. All responded to questionnaires about times taken to mark two of four samples of candidate responses. We demonstrated a positive practice effect for inexperienced markers, who became significantly faster during the course of their marking whilst maintaining their accuracies; there was no clear trade-off between speed and accuracy. The benefits of marking practice and background experience are distinct phenomena. To improve accuracy, longer term investments in education and experience are needed.