Rare decays at LHCb

Using $1.0 \mbox{fb}^{-1}$ of LHCb data searches for the rare decays $B^0_{(s)} \to \mu^+\mu^-$, $B^0_{(s)} \to \mu^+\mu^- \mu^+\mu^-$ and $\tau^- \to \mu^+\mu^- \mu^-$ are presented, also a search for $D^0 \to \mu^+\mu^-$ using $0.9\mbox{fb}^{-1}$ of LHCb data is discussed. In the absence of an excess of events upper limits are set on each decay mode. An angular analysis of $B^0 \to K^{*0}\mu^+\mu^-$ and the isospin asymmetries in $B \to K^{(*)} \mu^+\mu^-$ are measured using $1.0 \mbox{fb}^{-1}$ of LHCb data, measurement of the angular and isospin observables as a function of the invariant mass of the muon pairs are made.