Abstract Hoarding, the repetitive collection of excessive quantities of poorly useable items of little or no value with failure to discard these items over time, is characterized in DSM-IV as a symptom of obsessive–compulsive disorder (OCD) and obsessive–compulsive personality disorder (OCPD) but has, until recently, received scant empirical investigation. We describe the demographics, phenomenology, associated psychopathology and family history in 15 subjects presenting with hoarding behavior. Fifteen subjects were recruited from an OCD clinic and newspaper advertisement and assessed with the comprehensive Structured Clinical Interview for DSM-IV (SCID I and II), the Yale-Brown Obsessive Compulsive Scale (Y-BOCS), and a hoarding questionnaire (devised by the authors). The sample comprised 11 women and four men who hoarded a mean of seven item types, with a mean duration of 13.2 ± 3.9 years (range 2–15 years). Their mean age was 41.8 ± 14.3 years (range 20–65 years). The most common motive for hoarding was the fear of discarding items of practical value. Nine subjects met DSM-IV criteria for OCD, 9 met criteria for OCPD, for symptoms and behaviors other than hoarding, while six subjects met criteria for a putative OCD spectrum disorder (Tourette's, body dysmorphic disorder, trichotillomania). Six subjects reported little or no control over their hoarding, but only one subject saw her symptoms as an ‘illness’ warranting treatment. Pathological hoarding is usually a covert and chronic behavior causing distress and/or impairment, and may be related to OCD and OCPD. Hoarding may meet the criterion for a compulsion in DSM-IV, yet there is evidence to suggest that hoarding may manifest in a variety of other psychiatric conditions. While a range of pharmacologic and behavioral treatments have been tried, their effectiveness in managing hoarding behaviors requires additional research.