The effect of uncertainty in composite material properties on the cross-sectional stiffness properties, natural frequencies and aeroelastic response of a composite helicopter rotor blade is investigated using numerical simulations. The elastic modulii and Poisson's ratio of the composite material are considered as random variables with co-efficient of variation around 5 percent. A finite element method based on variational asymptotic procedure is used for evaluating the blade cross-sectional properties. Aeroelastic analysis based on finite element in space and time is used to evaluate the helicopter blade response in forward flight. The stochastic cross-sectional and aeroelastic analysis are carried out with Monte Carlo simulations. It is found that the blade cross-sectional stiffness show a co-efficient of variation of about 12 percent. The fundamental rotating natural frequencies of the rotor blade show a co-efficient of variation of 0.63, 5.62 and 5.07 percent for flap, lag and torsion, respectively. The impact of material uncertainty on rotating natural frequencies varies with the influence of centrifugal stiffening over structural stiffness for flap, lag and torsional motions. Further, the stochastic rotating natural frequencies show a chance of coinciding with the integer multiples of the rotor speed. The propagation of material uncertainty into aeroelastic response cause large deviations from the baseline response. The vibratory 4/rev loads acting on the rotor hub show a considerable deviation from the baseline predictions because of the material uncertainty. The numerical results clearly show the need to consider randomness of composite material properties in the helicopter aeroelastic analysis, design and optimization.