The objective of this paper is to determine the whirling bending critical speeds of pultruded composite shafts in simply supported boundary conditions. Theoretical studies have been carried using Patran to determine the natural frequencies and the mode shapes for the Jeffcot and Kikuchi rigid rotor models. A tabletop experimental apparatus has been fabricated and the bending critical speeds have been measured for various span lengths between the supports. The results of this study may be useful in identifying whether pultruded composite shafts can be employed as drive shafts in automotive or other industries.