Knowledge of the exact spatial distribution of brain tissues in images acquired by magnetic resonance imaging (MRI) is necessary to measure and compare the performance of segmentation algorithms. Currently available physical phantoms do not satisfy this requirement. State-of-the-art digital brain phantoms also fall short because they do not handle separately anatomical structures (e.g. basal ganglia) and provide relatively rough simulations of tissue fine structure and inhomogeneity. We present a software procedure for the construction of a realistic MRI digital brain phantom. The phantom consists of hydrogen nuclear magnetic resonance spin–lattice relaxation rate (R1), spin–spin relaxation rate (R2), and proton density (PD) values for a 24 × 19 × 15.5 cm volume of a “normal” head. The phantom includes 17 normal tissues, each characterized by both mean value and variations in R1, R2, and PD. In addition …