Corporate responsibility has many facets. It can be viewed as an interaction with the society to the mutual benefit of both partners. A corporation produces goods or services that the society demands. Production should be conducted so that its environmental impact is minimal, the economic state of the corporation is viable, labor conditions are good, and compliance with laws and regulations is satisfactory, among others. A model is presented that uses hierarchical fuzzy reasoning that assesses a facet of corporate responsibility, called sustainability, given a number of inputs, called basic indicators. Inputs are normalized on a scale (0, 1) according to their sustainability status and then combined to obtain a sustainability index on (0, 1) for each facet of the corporation. A sensitivity analysis pinpoints the most important indicators affecting sustainability. Two case studies of multinational companies, one of which is headquartered in Greece, are presented in detail. Both are producers of cement and other related building materials.