During the late 1960s, cannabis emerged from relative obscurity to become the most common illicit drug used in the United States, and has remained so ever since. From an epidemiological perspective, three major waves of successively younger new users can be identified during the past 40 years. Contrary to popular opinion, cannabis use can be problematic for many people (particularly adolescents). Moreover, the drug has become increasingly more potent. Cannabis is currently one of the leading substances reported in arrests, emergency room admissions, autopsies and treatment admissions. Like alcohol and tobacco, the need for effective approaches to treating cannabis use disorders transcends debates about whether it should be legal. Moreover, the costs to society are continuing to mount from past neglect of this continuing public health problem. This paper provides background on the need to develop effective models for treating cannabis use disorders.