During the last three decades the constructed response format has gradually gained entry in large-scale assessments of reading-comprehension. In their 1991 Reading Literacy Study The International Association for the Evaluation of Educational Achievement (IEA) included constructed response items on an exploratory basis. Ten years later, in Progress in International Reading Literacy Study (PIRLS) 2001, the constructed response format is ascribed special significance as bearer of central insights to the definition of reading literacy. This article focuses on the significance of the scoring guides and the relation between these guides on the one hand, and the text and the items on the other hand. A discussion of this relation as it is to be found in PIRLS 2001 is performed, showing both examples of success and more problematic aspects in the operationalisation of the intentions expressed in the theoretical framework for the test. Handling the problem of semantic openness is essential in representing depth of understanding and represents a field of possibilities for further research and development. (Contains 3 tables and 8 notes.)