We report the development of an arm exercise test to assess breathlessness in patients with lung cancer who are breathless at low levels of exertion. Exercise consisted of raising the arm over 40 cm, either the dominant arm only (n=10) or both arms alternating at minute intervals (n=12). Subjects breathed through a mouthpiece, and ventilation (VE) and oxygen uptake (VO(2)) were measured. Following familiarization, three tests were performed over one week to explore repeatability, and sensitivity was assessed in a fourth test. Arm exercise was generally well tolerated and increased breathlessness, VE, and VO(2). The commonest factor limiting exercise was arm fatigue, although four patients in the two-arm test also reported breathlessness. Repeatability for breathlessness score and VE was best in the two-arm test. The added resistance used to assess sensitivity could not be detected. The two-arm test offers a potential means of assessing the effects of an intervention on breathlessness and E in patients for whom a cycle or treadmill exercise test is unsuitable.