An integrable asymmetric exclusion process with impurities is formulated. The model displays the full spectrum of the stochastic asymmetric XXZ chain plus new levels. We derive the Bethe equations and calculate the spectral gap for the totally asymmetric diffusion at half filling. While the standard asymmetric exclusion process without impurities belongs to the KPZ universality class with an exponent 3 2 , our model has a scaling exponent One-dimensional three-state quantum Hamiltonians and master equations of reaction-diffusion processes have played an important role in describing strongly correlated electrons and nonequilibrium statistical mechanics in the last decades, mainly due to their intrinsic and nontrivial many-body behavior. Remarkably, in one dimension several models in this category are exactly solvable, as the spin-1 Sutherland ͓1͔ and t-J ͓2͔ models, and the asymmetric diffusion of two types of particles ͓3͔. In its formulation in terms of particles with two global conservation laws, these models describe the dynamics of two types of particles on the lattice, where the total number of particles of each type is conserved separately. In order to ensure integrability, all known models in this class satisfy some particle-particle exchange symmetries ͓4,5͔. Recently, we introduced a new class of three-state model in the context of high-energy physics that is integrable despite it does not have particle-particle exchange symmetry ͓5͔. The quantum version is closely related to the strong regime of the t-U Hubbard model and the XXC model ͓6͔. In this work we formulate a stochastic model related to ͓5͔ that describes an asymmetric exclusion process ͑ASEP͒ with impurities. Although our model can be solved by the coordinate Bethe ansatz, we are going to formulate a matrix product ansatz ͑MPA͒ ͓4,7͔ due its simplicity and unifying implementation for arbitrary systems. This MPA introduced in ͓4,7͔ can be seen as a matrix product formulation of the coordinate Bethe ansatz and it is suited to describe all eigenstates of integrable models. We solve this model with periodic boundary condition through the MPA and we analyze the spectral gap for some special cases. Our model displays the full spectrum of the ASEP without impurities ͓8͔ plus new levels. The first excited state belongs to these new levels and has unusual scaling exponents. Although the ASEP without impurities belongs to the KPZ universality class ͓9͔ ͑dy-namic exponent 3 2 ͒, our model displays a scaling exponent 5 2 . The model we propose describes the dynamics of two types of particles ͑types 1 and 2͒ on the lattice, where the total number of particles of each type is conserved. In this model if the neighbor sites are empty, particles of type 1 can jump to the right or to the left with rates ⌫ 0 1 1 0 and ⌫ 1 0 0 1 , respectively. Particles of type 2 "impurities" do not jump to the neighbor sites if they are empty, but can change positions with neighbor particles of type 1 with rates ⌫ 2 1 1 2 and ⌫ 1 2 2 1 if particle 1 is on the left or on the ri...