Designing a definitive study is difficult without having an estimate of the likely size of effect, if this is large, as suggested by the one case report(Moses, Harper et al. 2006) a small number of patients are needed. If it is small as seems more likely a priori, a larger number of patients are needed requiring European collaboration and considerably greater funding. We therefore designed a pragmatic pilot study using a single geographic population with a simple, inexpensive protocol which will serve several functions, specifically to: (1) determine the optimum dose of doxycycline needed to suppress MMP production. (2) define the safety profile of doxycycline in LAM. (3) provide evidence of efficacy and size of effect. (4) provide data to help optimise the design and logistics of future trials.