Clinical observations and research show that symptom perception in asthma is, at worst, inaccurate or often biased in two directions: (1) blunted perception, (2) overperception (both involving airway obstruction manifested in low or high breathlessness). Theoretically breathlessness occurs during respiratory labor or blood gas changes. However, pathophysiological factors and asthma severity are inconsistently related to perceptual accuracy. Consequently, symptom perception within the biomedical perspective is not well understood. Possible psychological influences, varying from the stimulus level to emotions and high-order reasoning, are discussed.