Abstract Four constant and equal viscosity polymer solutions (Boger fluids) were constructed for comparable elongational property measurements. The common constant viscosity of the solutions was 0.20 Pa s while four polymers were chosen to range from rigid and slender to flexible coiled and enlarged molecules in solution. Comparative elongational measurements on the four solutions in the Newtonian (inelastic) solvents were made with a Rheometrics RFX opposed jet viscometer. The Trouton ratios observed for the polymer solvents and various water—glycerol solutions agreed to within ±30% of the expected Trouton ratio of 3, while the results for the rigid molecules in solution agreed with the Batchelor prediction based on the molecular aspect ratio determined independently for the polymer from light scattering measurements. This paper presents a direct comparison of extensional flow resistance of the several types of polymers: a rod-like polymer, a semi-rigid chain, a compact random coil, and a highly expanded random coil.