The prevalence of Mycobacterium avium complex (MAC) pulmonary disease is increasing globally. However, reliable national and international data relating to its epidemiology and management is lacking. During the period 2003-2014, MAC was isolated from the pulmonary samples of 75 patients at the Irish Mycobacteria Reference Laboratory (IMRL). Most patients (42, 56%) had underlying pulmonary disease, and 37 (49%) had clinical/radiographic characteristics consistent with MAC pulmonary disease. However, only 18 patients (24%) fulfilled internationally accepted criteria for diagnosis/treatment of this disease. Treatment was started in 13 (72%) of these cases, which is similar to internationally published treatment rates. The diagnosis of significant MAC pulmonary disease can be difficult, and treatment is not always warranted even when diagnostic criteria are met.