Gambling disorder is a frequently underdiagnosed and disabling disorder with a prevalence greatly increased in recent decades. For various reasons, only a small part of pathological gamblers seek a support making difficult an early identification and delaying the administration of appropriate treatment. In DSM-5, the disorder has been reclassified from an "Impulse-Control Disorder not elsewhere classified" to one of the "Substance-Related and Addictive Disorders" with the intention of improve the diagnosis, to better targeting the treatment and to stimulating further research efforts directed to the disorder. This article reviews assessment techniques, psychosocial and neurobiological factors in the development of pathological gambling and treatment strategies.