Context:The reliability of clinical techniques to quantify thoracic spine rotation range of motion (ROM) has not been evaluated.Objective: To determine the intratester and intertester reliability of 5 thoracic rotation measurement techniques.Design: Descriptive laboratory study. Setting: University research laboratory.Patients or Other Participants: Forty-six healthy volunteers (age=23.6±4.3 years, height=171.0±9.6 cm, mass= 71.4 ± 16.7 kg).Main Outcome Measure(s): We tested 5 thoracic rotation ROM techniques over 2 days: seated rotation (bar in back and front), half-kneeling rotation (bar in back and front), and lumbar-locked rotation. On day 1, 2 examiners obtained 2 sets of measurements (sessions 1, 2) to determine the within-session intertester reliability and within-day intratester reliability. A single examiner obtained measurements on day 2 (session 3) to determine the intratester reliability between days. Each technique was performed 3 times per side, and averages were used for data analysis. Reliability was determined using intraclass correlation coefficients, standard error of measurement (SEM), and minimal detectable change (MDC). Differences between raters during session 1 were determined using paired t tests.Results: Within-session intertester reliability estimates ranged from 0.85 to 0.94. Ranges for the SEM were 1.0°to 2.3°a nd for the MDC were 2.8°to 6.3°. No differences were seen between examiners during session 1 for seated rotation (bar in front, both sides), half-kneeling rotation (bar in front, left side), or the lumbar locked position (both sides) (all values of P> .05). Within-day intratester reliability estimates ranged from 0.86 to 0.95. Ranges for the SEM were 0.8°to 2.1°and for the MDC were 2.1°to 5.9°. Between-days intratester reliability estimates ranged from 0.84 to 0.91. Ranges for the SEM were 1.4°to 2.0°a nd for the MDC were 3.9°to 5.6°.Conclusions: All techniques had good reliability and low levels of measurement error. The seated rotation, bar in front, and lumbar-locked rotation tests may be used reliably when more than 1 examiner is obtaining measurements.Key Words: biomechanics, bubble inclinometer, goniometer, scapulothoracic joint Key Points• Within-session and between-sessions reliability values for the 2 examiners for each of the 5 thoracic rotation range-ofmotion measurement techniques were good. • All measurement techniques showed low SEM « 3°) and minimal detectable change « 6°) values for all techniques.• The seated rotation, bar in front, and lumbar-locked rotation tests did not display differences between examiners during session 1. These techniques may be used with confidence by clinicians and researchers.