Gambling has long been considered to constitute a recreational activity in most cultures worldwide. While most people gamble or have gambled at least once in their lifetime, only a minority proceeds to develop pathological gambling. Gambling addiction is typically observed in men, has an early onset and causes serious psychosocial and financial problems, and it displays a high rate of comorbidity with other mental disorders and addictions. The etiology of pathological gambling has not been yet elucidated, but there is evidence that it is a multifaceted illness, attributable to the interaction of individual and environmental factors. Recent research conclusions have resulted in substantial changes in the 5th version of the Diagnostic and Statistical Manual of Mental Disorders, with the incorporation of a wider category of addictions, namely "behavioral addictions", including "pathological gambling". The need for accuracy and clarity in the diagnosis of pathological gambling has led to the construction of various screening instruments with good psychometric properties. Substantial progress has also been documented in the treatment of gambling addiction, both pharmaceutical and psychotherapeutic. In recent years issues have emerged concerning pathological gambling in adolescents and young people, and the widespread availability of internet-based gambling opportunities, which require further investigation and better understanding of the processes involved.