Pulmonary actinomycosis is a rare but important and challenging diagnosis to make. Even when the clinical suspicion is high, the disease is commonly confused with other chronic suppurative lung diseases and with malignancy. An early, accurate diagnosis will prevent the considerable psychological and physical morbidity, including unwarranted surgery, associated with delayed diagnosis. The clinical, radiological and therapeutic characteristics of the infection are reviewed here. Respiratory physicians should be aware of this important differential when investigating patients for persistent pulmonary shadowing. This will expedite the diagnosis of an otherwise highly treatable condition with an excellent prognosis if picked up early.