It is demonstrated that surface plasmon sensing can be performed in the shot-noise-limited regime to resolve index of refractive changes on the order of 10-10/√Hz at input powers of 1 mW. This improved resolution is achieved by using active electronic noise cancelling to suppress laser intensity noise and a wavelength that maximizes sensitivity to index of refraction changes occurring at an interface. The resolution of the system is experimentally demonstrated by measuring the refractive index change of air in response to pressure changes.