CONTEXT: Dyspnea is a poorly understood subjective sensation. Existing dyspnea measures fail to adequately address its multidimensionality. A Japanese group developed and validated the Cancer Dyspnea Scale (CDS) for assessing dyspnea in patients with advanced lung cancer. OBJECTIVES: We evaluated the validity and reliability of the English version of the CDS (CDS-E) that has 12 items and takes, on average, 140 seconds for individuals to complete. METHODS: Eligible patients had advanced lung cancer, consented, and were fluent in English. Participants completed a 100 mm visual analogue scale (VAS), the modified Borg scale, the CDS-E, the Hospital Anxiety and Depression Scale, and the Functional Assessment of Cancer Therapy--Lung quality-of-life scale. Demographic, radiographic, and treatment information were obtained from patients' medical records. RESULTS: One hundred twelve participants were enrolled at three sites in the U.S., Australia, and the U.K. Mean age was 64.5 years (SD 11.5); 90% were Caucasian, 68% had Eastern Cooperative Oncology Group performance status 0-1, and 50% had non-small cell carcinoma. All completed the CDS-E independently, without difficulty. The CDS-E had reasonable internal consistency overall (Cronbach's α = 0.71) and for each of the three factors (effort, anxiety, discomfort Cronbach's α = 0.80-0.84). CDS-E scores were significantly correlated with the 100mm VAS (r = 0.82; P < 0.001) and the modified Borg (r = 0.87; P < 0.001). After factor analysis, the CDS-E was revised by removing three items (r-CDS-E). CONCLUSION: The CDS-E and r-CDS-E are reliable and valid measures of the sensation and the psychological components of dyspnea, with the shorter version having similar psychometric properties.