This study investigates the effect of randomness in composite material properties on the aeroelastic analysis predictions. The impact of material uncertainty on the cross-sectional stiffness, natural frequencies and aeroelastic response predictions of a composite helicopter rotor blade are studied. The elastic modulii and Poisson's ratio of the composite plies are considered as random variables with a coefficient of variation of 5 percent. An analytical model is used for evaluating blade cross-sectional stiffness. Aeroelastic analysis based on finite elements in space and time is used to evaluate the helicopter rotor blade response in hover. The stochastic cross-sectional and aeroelastic analyses are carried out with Monte Carlo simulations. The blade cross-sectional stiffness matrix elements show a coefficient of variation of about 9 percent. The impact of material uncertainty on rotating natural frequencies varies with the lag, flap and torsional motions because of centrifugal stiffening. The blade tip response in hover show a considerable scattering from the baseline value. The numerical results clearly show the need to consider randomness of composite material properties in the helicopter aeroelastic analysis.