The paper deals with the problem of fatigue crack growth under variable-amplitude loading from a lifetime prediction viewpoint. A sequential Monte Carlo technique is employed to monitor crack propagation in presence of several uncertainties related to the material properties, measurement systems and environmental variability. The algorithm is able to estimate the most probable parameters describing crack growth data focusing on the most probable crack growth trajectories and enhancing the prediction of the residual life of the structure. Monte Carlo sampling allows accounting for the variable amplitude loading condition, simulating several crack growth evolutions using different loads and selecting the more appropriate for the actual crack evolution. The outcome of the algorithm that is the residual life prediction is used to appreciate the performances of the method. The end of the paper discusses the application of the method within structural health monitoring systems and lifetime predictor frameworks.