Abstract
In this paper we consider the influence of trans-Planckian physics on the CMBR anisotropies produced by inflation. We consider a simple toy model that allows for analytic calculations and argue on general grounds, based on ambiguities in the choice of vacuum, that effects are expected with a magnitude of the order of H/Λ, where H is the Hubble constant during inflation and Λ the scale for new physics, e.g., the Planck scale.