Recently, a considerable number of object-oriented software development methods have been introduced to produce extensible, reusable, and robust software. We have been involved in the development of a large number of pilot applications to form our own view on object-oriented methods. Although our experiences confirmed the claims about the benefits of object-oriented methods, we identified a number of important obstacles that are not addressed by current methods. This paper summarizes these obstacles and evaluates them with respect to our pilot applications. The aim of this paper is to make software engineers aware of problems they may encounter during object-oriented development, and to inspire researchers to initiate new research activities.