Abstract. The increasing computational load required by most applications and the limits in hardware performances affecting scientific computing contributed in the last decades to the development of parallel software and architectures. In Fluid-Structure Interaction (FSI, in short) for haemodynamic applications, parallelization and scalability are key issues (see [20]). In this work we introduce a class of parallel preconditioners for the FSI problem obtained by exploiting the block-structure of the linear system. We stress the possibility of extending the approach to a general linear system with a block-structure, then we provide a bound in the condition number of the preconditioned system in terms of the conditioning of the preconditioned diagonal blocks, finally we show that the construction and evaluation of the devised preconditioner is modular. The preconditioners are tested on a benchmark 3D geometry discretized in both a coarse and a fine mesh, as well as on two physiological aorta geometries. The simulations that we have performed show an advantage in using the block preconditioners introduced and confirm our theoretical results.Key words. Blood-Flow Models , Fluid-Structure Interaction , Finite Elements , Preconditioners , Parallel Algorithms AMS subject classifications. 65M60 , 65F08 , 65Y05 , 76Z051. Introduction . The modeling of the cardiovascular system is receiving increasing attention from both the medical and mathematical environments because of, from the one hand, the great influence of haemodynamics on cardiovascular diseases ([20] chap 1), and, from the other hand, its challenging complexity that keeps open the debate about the setting up of appropriate models and algorithms. A wide variety of approaches can be found in literature, dealing with different formulations of the problem and solution strategies.In this introduction we refrain from describing the models that can be used to simulate the physiological behavior of the arterial vessels; for that we address the interested reader to [20]. We give instead an overview of some of the most popular methodologies to solve numerically the coupled system of equations arising from the haemodynamic model: those that describe the flowfield variables (blood velocity and pressure) and those that govern the mechanical deformation of the vessel walls (the "structure"). The first distinction comes from the formulation of the problem.A common choice in the FSI context is to describe the fluid equations using an Arbitrary Lagrangian-Eulerian frame of reference (see e.g. [31]). The advantage with respect to an Eulerian description is that the coupling can be satisfied exactly on the fluid-structure interface. However the introduction of a new equation for the fluid domain motion is required, and its dependence on the solution of the FSI problem introduces a further nonlinearity.A different approach consists of a space-time formulation which adopts the Eulerian framework. Usually, the latter involves a discretization of the computational domain in time slab...