Fatigue damage accumulation and failure of steel reinforcement bars (rebars) is a stochastic process. Scatter can be influenced by the sensitivity of the short crack growth to the microstructural features, especially near the fatigue limit. This work investigates the scatter inherent to the microscopic conditions near the fatigue limit of ferrite-pearlite and martensite microstructures found in the outer layer of rebars. An adapted Navarro-De Los Rios model within a Monte-Carlo framework is used to simulate the short crack growth in material grains. Grain size variation, grain orientation factor and multiple phases i.e., ferrite-pearlite and martensite were considered in the model. The results are compared with the scatter found in fatigue tests on hot-rolled-cold worked (HR-CW) as well as quenched and tempered (QST) rebars. It is shown that microstructural effects explains part of the observed scatter in the fatigue tests. (C) 2015 Elsevier Ltd. All rights reserved.