Unexplained dyspnoea is defined as a chronic (≥ 3 months) and significant (mMRC ≥ 2) dyspnoea without a diagnosis after clinical examination, chest X-ray, biological work-up and electrocardiogram. This condition affects 15 % of patients with dyspnoea and is associated with prolonged diagnostic delay and difficulties in patient referral. This article presents the definition and epidemiology of unexplained dyspnoea, as well as the useful elements of the history and clinical examination. It covers the specific differential diagnosis and proposes a diagnostic algorithm for the primary care physician. Finally, it discusses possible developments in this field to improve the management of these patients.