Tuberous sclerosis (TSC) is an inherited disorder best known for its association with severe learning difficulties, epilepsy, behavioural problems, skin and renal pathology Lymphangioleiomyomatosis (LAM), characterized by alveolar smooth muscle proliferation and cystic destruction of parenchyma, occurs as an infrequent symptomatic pulmonary complication in TSC and as a very rare sporadic disease in those without signs of TSC. Considered a generalized and progressive cystic lung disease that is difficult to treat with a poor prognosis, it has been reported almost exclusively in women, most commonly presenting with dyspnoea and pneumothorax in those of childbearing age. We investigated the clinical features and prognosis of LAM in patients with TSC including the effects of treatment, stratified by the method of diagnosis of LAM (i.e. histological or radiological). We found histological proof of diagnosis in 10 of 21 patients with TSC and symptomatic lung disease, onset in childhood in four, three males with LAM, individuals with apparently focal disease, great variation in clinical course and no clear treatment benefit. In those with TSC, symptomatic LAM is infrequent but causes a significant morbidity and mortality It was not possible to detect predisposing factors, other than being female. Males with apparent LAM should be rigorously investigated.