Using a Markov chain approach we rederive the exact density functional for hard rod mixtures on a one-dimensional lattice, which forms the basis of the lattice fundamental measure theory. The transition probability in the Markov chain depends on a set of occupation numbers, which reflects the property of a zero-dimensional cavity to hold at most one particle. For given mean occupation numbers (density profile), an exact expression for the equilibrium distribution of microstates is obtained, that means an expression for the unique external potential that generates the density profile in equilibrium. By considering the rod ends to fall onto lattice sites, the mixture is always additive. In 2002 Lafuente and Cuesta extended Rosenfeld's fundamental measure theory to lattice models based on a derivation of an exact density functional for hard rod mixtures in one dimension [16,17]. This derivation was carried out following a procedure developed by Vanderlick et al.[18] for continuum fluids. Since the excess free energy part of the functional could be expressed in terms of differences between parts that agree in their functional form with the excess free energy functional of a zerodimensional cavity, approximate functionals in higher dimensions were obtained by dimensional expansion of the corresponding difference operator. By construction these fundamental measure functionals have the property to become exact under dimensional reduction and their impressive power was first shown by determining phase diagrams of hard squares [17,19] and hard cube mixtures [16,17,20] with good quality. The fundamental measure functionals moreover allow one to apply the method of dimensional crossover and the merit of this was demonstrated by deriving functionals for lattice gases with nearest neighbor exclusion for different lattice types (square, triangular, face-and body-centered cubic) from the functional for cubes in (d + 1) dimensions [21]. The structure of the corresponding results led to a suggestion how to construct fundamental measure functionals for hard core lattice gases for any type of lattice, shape of the particles, and arbitrary dimension [22].In this report we rederive the exact density functional for hard rod mixtures in one dimension, that means the * philipp.maass@uni-osnabrueck.de