The findings from recent University of Illinois investigations on the effects of icing on airfoil aerodynamics were reviewed. The review was also supplemented with data that currently exist in the literature in order to provide a more complete analysis. Increasing the ice shape height generally resulted in more severe performance degradations. The variations in geometry of the simulated ice had some effects on airfoil aerodynamics. Iced-airfoil aerodynamics were relatively insensitive to Reynolds number variations. The most severe performance penalties were observed when the simulated ice was located near the adverse pressure recovery region of the clean model. Because of this, airfoil geometry plays an important role in iced-airfoil aerodynamics.