Ecstasy/3,4 Methylenedioxymethamphetamine is a popular recreational drug that is a potent indirect monoaminergic agonist that has structural similarities to mescaline and amphetamine. It is presumed that interfering with regulatory serotonin signalling with chronic ecstasy use may result in psychobiological harm. This chapter reviews evidence from studies assessing mood, cognition, pain, sleep and neuroendocrine function, in addition to molecular, structural and functional neuroimaging to assess functional and neural evidence of psychobiological harm. Declarative memory requires conscious recall of memory. Both immediate and delayed recall are areas that appear to consistently show deficits associated with ecstasy use. Ecstasy users show generalised prospective memory difficulties that have implications for everyday functioning. The chapter summarises the literature investigating executive performance in ecstasy users relative to controls. Miyake et al.'s initial influential framework of executive function suggested that separable executive functions were: 'mental set switching', 'inhibitory control' and 'memory updating'.