This paper describes the phenomenological features of early childhood onset obsessive compulsive disorder (OCD; defined as children meeting DSM-IV criteria for OCD with age of onset <8 years). Fifty-eight children (ages 4-8) were included in the sample. OCD and comorbid diagnoses were determined by structured interview, and OCD severity was measured using the Children's Yale-Brown Obsessive Compulsive Scale (CY-BOCS). Mean age of OCD onset was almost five, and mean age of presentation was between 6 and 7. Mean symptom severity was in the moderately severe range. Comorbidity and family history of OCD were common. Contamination and aggressive/catastrophic obsessions and washing and checking compulsions were endorsed most frequently. Results indicate that early childhood onset OCD may have a lower boy to girl ratio and lower rates of depressive disorders, but may be similar to later childhood onset OCD in terms of OCD symptom presentation and severity.