OBJECTIVES: ISPOR has focused on patient reported outcomes (PROs) since the second annual European Congress in 1998, but the prevalence of PROs in product evaluation for Health Technology Assessments (HTAs) is not well studied.  This study examines the prevalence of PROs for reviews published by nine agencies in 2005-2011: PBAC, CADTH, HAS, IQWiG, SMC, NHS Scotland, NICE, DERP, AHRQ.   METHODS: Analysis of all HTA reports from 2005-2011 in the aforementioned agencies for 13 disease areas: Alzheimer’s Disease, Anemia in Cancer and Chronic Kidney Disease, Chronic Myelogenous Leukemia, Clostridium Difficile, Depression, Diabetes, Glaucoma, Hepatitis C (adults and pediatrics), HIV (adults and pediatrics), HPV, Osteoporosis, Ovarian Cancer, Parkinson’s Disease.  RESULTS: Among the 324 total reviews from 2005-2011, 91 (28%) reviews report PROs. The use of PROs increased steadily, from 11.1% in 2005 to 42.5% in 2011.  We find wide variation across disease conditions and agencies in the use of PROs.  For several disease conditions there is no use of PROs, but Anemia in Cancer, Ovarian Cancer and Parkinson’s Disease reviews use PROs at least 75% of the time.  Use by agencies varies from 9.8% (HAS) to 66.7% (IQWiG; NHS Scotland). Reviews of disease conditions are distributed unequally across agencies and vice versa. This raises the possibility that agencies’ differing use of PROs might simply reflect differences across disease conditions in PRO use, or the reverse.  We find evidence that agencies tend to behave differently depending on the disease condition under review. A significant part of the variation across agencies arises from their emphasis on different disease conditions. CONCLUSIONS: HTAs use PROs as an evaluator less than a third of the time.  The use of PROs is steadily increasing over time.  Therapeutic area drives the use of PROs.