This paper describes an experiment to assess the impact of inheritance on the modifiability of object- oriented business domain models. This experiment is part of a research project on the quality determinants of early systems development artefacts, with a special focus on the maintainability of business domain models. Currently there is little empirical information about the relationship between the size, structural and behavioural properties of business domain models and their maintainability. The situation is different in object-oriented software engineering where a number of experimental investigations into the maintainability of object-oriented software have been conducted. The results of our experiment indicate that extensive use of inheritance leads to models that are more difficult to modify. These findings are in line with the conclusions drawn from three similar controlled experiments on inheritance and modifiability of object-oriented software.