Rationale: It is hypothesized that the affective dimension of dyspnea (unpleasantness, emotional response) is not strictly dependent on the intensity of dyspnea. Objectives: We tested the hypothesis that the ratio of immediate unpleasantness (A₁) to sensory intensity (SI) varies depending on the type of dyspnea. Methods: Twelve healthy subjects experienced three stimuli: Stimulus 1: maximal eucapnic voluntary hyperpnea against inspiratory resistance, requiring 15 times the work of resting breathing. Stimulus 2: PET _CO2 6.1 Torr above resting with ventilation restricted to less than spontaneous breathing. Stimulus 3: PET _CO2 7.7 Torr above resting with ventilation further restricted. After each trial, subjects rated SI, A₁, and qualities of dyspnea (SQ) on the Multi-Dimensional Dyspnea Profile (MDP), a comprehensive instrument tested here for the first time. Results: Stimulus 1 was always limited by subjects failing to meet a higher ventilation target; none signaled severe discomfort; this evoked work and effort sensations, with relatively low unpleasantness (mean A₁/SI=0.64); Stimulus 2, titrated to produce dyspnea ratings similar to those subjects gave during Stimulus 1, evoked air hunger and produced significantly greater unpleasantness (mean A₁/SI = 0.95); Stimulus 3, increased until air hunger was intolerable, evoked the highest intensity and unpleasantness ratings and high unpleasantness ratio (mean A₁/SI=1.09). When asked which they would prefer to repeat, all subjects chose Stimulus 1. Conclusions: 1) Maximal respiratory work is less unpleasant than moderately intense air hunger in this brief test; 2) Unpleasantness of dyspnea can vary independently from perceived intensity, consistent with the prevailing model of pain; 3) Separate dimensions of dyspnea can be measured with the MDP.