This Comment explains why current practices in the patent examination process provide inadequate guidance when dealing with open-ended product claims. This lack of guidance, as argued in this Comment, could lead to patent examiners granting an overly broad scope to open-ended product claims, a breadth of scope that undermines fundamental patent law policies. This Comment proposes an alternative approach for the Patent and Trademark Office, an approach that suggests that examiners presumptively reject open-ended product claims in the unpredictable arts, such as chemistry.