Flows which were predominantly uniaxial in extension were generated through 0.5 mm diameter aligned jets. The torque required to keep the jets at a fixed distance apart, and thus the apparent stress generated by the fluid, was measured by a torque rebalance transducer attached to one of the moveable jet arms. Strain rates from 1000 to 20 000 s-1 were spanned. Data are presented for 1 to approximately 150 centipoise (cP) Newtonian water and glycerol/water mixtures. The trends found were consistent with a contribution to the measured torque by the inertia of the fluid, becoming negligibly small as the shear viscosity of the fluid approached approximately 75 cP. A method for correcting opposing-jet measurements made on fluids of viscosity less than 75 cP is described and the extent of the correction illustrated on a series of solutions with identical shear viscosities prepared from polyethylene glycols of molecular weight 8 x 10(3) to 1 x 10(6). The validity of the correction method for use on non-Newtonian fluids is discussed. The corrected results for the polyethylene glycol solutions of identical shear viscosity clearly illustrate the influence of molecular weight on extensional flow properties.