OBJECTIVES: To appreciate the effectiveness of treatments that reduce the frequency or severity of chronic obstructive pulmonary disease (COPD) exacerbations, the quality of life gains that result from this reduction should be adequately included. In the current study we evaluated the ability of the EQ-5D to reflect the course of a moderate exacerbation. METHODS: The study was designed as a prospective cohort study in which the change in EQ-5D scores over a period of 6 weeks was studied. 59 US patients, 40 year or older visiting the clinic with a moderate exacerbation were seen 4 times, i.e. during the screening visit and approximately 8, 14 and 43 days thereafter. Patients completed the EQ-5D at each visit. ‘Baseline’ EQ-5D was defined as the lowest of EQ-5D scores at visit 1 and 2, to capture the point at which the impact of the exacerbation is most severe. Standardized Response Mean (SRM) was calculated as the change divided by the standard deviation of change. RESULTS: The mean EQ-5D VAS and utility scores at baseline were 37 (SD 25; range 1-85) and 0.68 (SD: 0.21; range 0.17 to 1.00), respectively. Estimated improvements in VAS scores at visit 3 and 4 were 11.8 (p=0.0012) and 13.9 (p<0.0001), respectively. Estimated changes in utility scores were 0.1607 (p<0.0001) and 0.1534 (p<0.0001), respectively. SRM for EQ-5D utilities was 0.65, which was comparable with SRMs for symptoms (cough: 0.587, dyspnea 0.638). Patients with improvement in peak flow above the median had a larger improvement in utility (p=0.030) and VAS (p=0.012) than patients with improvement below the median. Based on curve estimation, an exacerbation results in average loss of 0.00188 QALY, compared to the same period with no exacerbation and 0.0286 compared to perfect health. CONCLUSIONS: EQ-5D VAS and utility are responsive to recovery from a moderate exacerbation, but changes are small.