In this presentation, we focuson the adjoint equation in fluid-structure interaction. Derivations for both stationary and nonstationary settings are undertaken. In the latter, the adjoint is running backward-in-time and must access the primal solution due to the nonlinearities.This is a computational challenge, but it is shown that the overall implementationis very promising and numerically robust. We demonstrate the performance in terms of error estimation, space/time adaptivity,and optimal control.