Lymphoangioleiomyomatosis (LAM) is a characteristic diffuse proliferation of abnormal smooth muscle fibers predominantly developing in the lung and leading to cystic destruction. An almost totally specific marker, HMB45, is available. This monoclonal antibody labels cells of the melanocyte line, LAM cells and renal angiomyolipoma cells. The antigen carried by all these cell lines is probably gp-100 involved in melanogenesis. Two gene loci are formally implicated in the pathogenesis of Bourneville tuberous sclerosis (BTS): TSC1 (9q 34.3) and TSC2 (16p 13.3). The TSC2 locus could be implicated in the pathogenesis of pulmonary LAM. LAM and BTS have similar clinical and histological features and could be two different phenotypic forms, distinguished strictly on a nosological basis, of the same disease. The hormone-dependence theory is suggested on the basis of purely clinical arguments, particularly the almost exclusive female predominance, generally during the period of genital activity. Certain counter arguments have also been put forward and consequently, since no in vitro cell culture model or animal model of LAM is available, it is not really possible to verify the hypothesis. Epidemiological data have been recently acquired in France with the constitution of the GERM"O"P registry of LAM cases in France. Recent technological progress in imaging techniques has also been helpful for earlier, more precise diagnosis. HMB45 immunolabeling improves diagnostic sensitivity on small tissue fragments obtained with transbronchial biopsies. The course of LAM appears to be different in certain patient subgroups. Certain patients develop rapidly fatal disease in months or years while in the majority of patients the disease is much less aggressive for years. A minority of patients also have very slowly evolving disease sometimes diagnosed after menopause. Lung transplantation remains the ultimate treatment in case of life-threatening prognosis.