IMPORTANCE:Knowledge regarding the reliability of pegboard tests when used to measure dexterity in people with Parkinson's disease (PD) is currently limited. OBJECTIVE:To examine the test-retest and interrater reliability of the 9-Hole Peg Test (9HPT) and Purdue Pegboard Test (PPT) in people with PD. DESIGN:Cross-sectional observational study. For test-retest reliability, tests were completed on 2 days, 1 wk apart, in the "on" phase and "end-of-dose" period of participants' medication cycle. For interrater reliability, occupational therapists and physical therapists rated prerecorded pegboard test performance of participants with PD. SETTING:Test-retest reliability was determined in participants' homes or in a university department. Interrater reliability was determined in a university department or a hospital setting. PARTICIPANTS:Test-retest reliability was determined with volunteers diagnosed with PD (N = 30). Interrater reliability was determined with a convenience sample of occupational and physical therapists (N = 11). OUTCOMES AND MEASURES:The 9HPT and PPT are commonly used measures of manual dexterity. RESULTS:PPT subtests showed higher test-retest reliability (intraclass correlation coefficients [ICCs] ≥ .90) in both phases of the medication cycle compared with the 9HPT (ICCs = .70-.81). Minimal detectable change scores indicated acceptable measurement error for both tools. Interrater reliability for recorded performance of each measure was very good (ICCs > .99), with no calculable measurement error. CONCLUSIONS AND RELEVANCE:Although both tools showed adequate test-retest and interrater reliability, results suggest that the PPT may be a more reliable measure of dexterity loss in people with PD. WHAT THIS ARTICLE ADDS:This study informs the clinical measurement of the loss of manual dexterity in people with PD, a frequent problem reported by people living with this disorder.