In learning complex material, one must first understand the material, after which learning and remembering follow automatically. The conventional psychological literature says little about the processes involved in the learning of complex material which may take weeks, months, or years to be learned, although most adult learning is of this form. The paper examines some of the issues that are involved in this type of learning, issues such as the nature of understanding, the types of hypotheses that subjects bring to bear on the learning process, and the types of processes that need to be studied in order to understand the psychology of learning.