Obsessive-compulsive spectrum disorders comprise a unique category of related disorders with important diagnostic, aetiological and therapeutic implications. This group of disorders may overlap with obsessive-compulsive disorder (OCD) in symptomatic profile, demographics, family history, neurobiology, comorbidity, clinical course and response to selective anti-obsessional behavioural and pharmacotherapies. OCD-related disorders can be viewed along a continuum with risk avoidance on the compulsive end and risk seeking at the other. This dimension may be defined within a framework which relates hyperfrontality and increased serotonergic sensitivity with compulsive disorders and hyperfrontality and low presynaptic serotonergic levels with impulsive disorders. Most biological models of OCD-related disorders stress the importance of serotonin in their pathophysiology and these disorders have also been shown to be preferentially responsive to selective serotonergic reuptake inhibitors (SSRIs). This paper reviews the management of the OCD spectrum and the evidence for efficacy of the SSRIs and the differential treatment responses of the compulsive and impulsive disorders with regard to therapeutic dosage, response lag time and maintenance of symptom remission.