In the present work viscosity data for three different samples with two different purity grades of diisodecyl phthalate (DIDP) are reported from 303.15 K to 373.15 K up to 60 MPa, together with density values from 283.15 K to 398.15 K and up to 70 MPa. The experimental measurements have been performed with a rotational automated viscometer Anton Paar Stabinger SVM3000, a rolling-ball viscometer Ruska 1602830 for high pressures and a recently automated Anton Paar DMA HPM vibrating-tube densimeter. The measured data for viscosity have been compared with previous literature values and could be useful to establish together with previous viscosity data, a correlation of the full viscosity surface eta(T, P) of DIDP. This correlation is needed for the calibration and verification of high-pressure viscometers at moderate viscosities. (C) 2009 Elsevier Ltd. All rights reserved.