The viscometric functions (eta, N-1 and N-2) for non-colloidal suspensions of spheres in a Boger fluid matrix were measured. Volume fractions (phi) of 5%, 10% and 20% were investigated. The relative viscosity (eta r = eta/eta(0)) and the (positive) first normal stress difference N-1 showed increases with phi which were larger than the dilute suspension theory predictions of 1 + 2.5 phi, indicating semi-dilute suspension behaviour. The main interest centres on the second normal stress difference N-2. The matrix fluid showed a zero second normal stress difference, and the measurements showed that N-2 was always negative for the suspensions. This agrees with the dilute suspension prediction found using the Landau-Lifschitz averaging procedure, but not with the ensemble averaging method, which predicts a positive N-2. Possible causes for this result are discussed. (C) 2013 Elsevier B.V. All rights reserved.