Objective: To compare patient-reported health care resource use (HCRU) and workplace productivity in patients diagnosed with ITP vs. a matched control group without ITP. Chronic Immune (Idiopathic) Thrombocytopenic Purpura (ITP) is an auto-immune disorder characterized by persistent thrombocytopenia (peripheral blood platelet count <150x109/L). Symptoms can range from spontaneous bleeding and bruising to intercranial bleeding. Corticosteroids are first line treatment with splenectomy in 2nd or 3rd line. Methods: ITP patients were sampled from the Platelet Disorder Support Association's database of approximately 14,000 ITP patients. ITP patients were selected if diagnosed by a physician for ITP and =18 years. The control group was =18 years, never diagnosed with ITP, and matched on socioeconomic factors, age and gender. Participants completed a cross-sectional internet survey including health resource use, employment, sick leave, and workplace productivity-related questions. Ttesting was performed with t-tests for continuous variables and chi-square for categorical variables. Results: A total of 1002 ITP patients and 1031 control subjects completed the survey between March 28 and April 3, 2006. Seventy-six percent were female and the mean age was 48; 42% of ITP patients vs. 26% of control group (p<0.05) had one or more visits each month to a specialty physician. Sixty-five percent of ITP patients were employed vs. 62% of control group. Of individuals employed, 53% of ITP patients took extended sick leave (= 1 week) vs. 28% of control, 38% of ITP patients had difficulty concentrating at work vs. 29% of control, and 25% of ITP patients could not complete normal work responsibilities vs. 18% of control (p<0.05 for all comparisons). Conclusion: The impact of ITP on HCRU in all ITP patients and workplace productivity in employed ITP patients is significant. ITP is burdensome to patients, impairing employed ITP patients in completing normal work responsibilities, and increasing extended time off from work and physician visits.