OBJECTIVES: Early morning symptoms impact the quality of life of patients with chronic obstructive pulmonary disease (COPD). The Early Morning Symptoms of COPD Instrument (EMSCI) was designed to measure the occurrence and severity of early morning symptoms in patients with COPD and the impact of those symptoms on activity limitation and rescue medication use. This abstract describes the psychometric analysis conducted to examine the EMSCI’s reliability and validity. METHODS: Psychometric properties were examined using data from a phase 3 clinical trial. Item analyses were conducted using data from the baseline week (weekly average) as well as the morning of Day 1 (both time points prior to first dose) from a random split half sample, stratified by baseline GOLD status. Descriptive statistics, factor analysis, and Rasch model analysis were conducted to examine item performance and final items were selected. Test-retest reliability was assessed for the final instrument using intra-class coefficient (ICC). Correlations with baseline assessments including the St. George Respiratory Questionnaire (SGRQ), Exacerbations of Chronic Obstructive Pulmonary Disease Tool - Respiratory Symptoms (EXACT-RS), and forced expiratory volume in 1 second (FEV) were used to evaluate concurrent validity.  RESULTS: Patients in the sample (N=1663) were aged 40-93 years (mean 63.93 ± 8.89) and 53% male. About 31% of patients experienced early morning symptoms that were at least moderate in severity on Day 1. A one-factor structure was confirmed with factor analysis for symptom severity items. Test-retest reliability was confirmed with symptom severity (ICC=0.84), activity limitation (ICC=0.85) and rescue medication (ICC=0.62). Concurrent validity was supported by the EMSCI’s significant positive correlation with both the SGRQ and EXACT-RS. CONCLUSIONS: Results suggest that the EMSCI is a reliable and valid instrument to evaluate early morning symptoms in COPD and can potentially be used to collect data to support clinical study endpoints.