AbstractThere are two distinct notions of validation for software measures. On the one hand there is the informal notion that a measure is only valid if it is useful and practical. Although this view of validation is important, it is almost impossible to test. On the other hand there is a formal notion of validation of measures and it is this view which is addressed here. By considering software measures in the context of measurement theory, and by considering a classification of software entities into products, processes and resources the paper describes what the authors believe are the necessary (but not sufficient) activities required for validation, and show how far this deviates from the ‘accepted’ view of validation.