Expiratory flow limitation and dyspnea during resting breathing are common in patients with severe chronic obstructive pulmonary disease (COPD). Although single lung transplantation (SLT) is used to treat end-stage COPD, its effects on flow limitation and dyspnea are not well established. We assessed expiratory flow-limitation and dyspnea in 13 COPD patients after SLT at rest in the sitting and supine positions by applying negative pressure at the mouth during tidal expiration (negative expiratory pressure [NEP] technique). If NEP increases flow throughout the control tidal volume (VT), flow limitation is absent (not flow limited [NEL]). If NEP does not increase flow during part of the control VT, flow limitation is present. After SLT, lung function improved in all but one patient. Twelve patients were NFL during resting breathing in both positions studied. The patient whose lung function did not improve after SLT was flow-limited (FL) both when seated and supine. This patient also exhibited moderately severe chronic dyspnea (Medical Research Council [MRC] score = 3). In the nine other patients in whom dyspnea was assessed, it was slight (MRC score = 1). In conclusion, after SLT for end-stage COPD, expiratory flow limitation at rest is uncommon in both the seated and supine positions. This is consistent with the finding that after SLT the degree of chronic dyspnea is generally slight.