Inspecting OO designs is an important way of ensuring the quality of software under development. When high-level design activities are finished, the design documents can be inspected to verify whether they are consistent among themselves and whether the software requirements were correctly and completely captured. This paper discusses some issues regarding the definition and application of reading techniques (i.e. procedural guidelines that can be given to inspectors) to inspect high-level OO design documents. An initial set of OO Reading Techniques and their experimental evaluation is described. A method for evaluating the reading techniques in more detail, i.e. Observational Techniques, is then presented, and experiences with its use are discussed. Through these discussions, we show how the reading techniques have evolved in response to empirical evidence (both qualitative and quantitative) regarding their use in practice. The complete and current set of techniques can be found in the appendices. (Also cross-referenced as UMIACS-TR-99-63)