(P,rho,T) data of 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide [EMIM][NTf(2)] at T = (283.15 to 373.15) K and pressures up to p = 100 MPa are reported with an estimated experimental relative combined standard uncertainty of Delta rho/rho = +/- (0.01 to 0.08) % in density. The measurements were carried out with a newly constructed Anton Paar DMA HPM vibration-tube densimeter. The system was calibrated using double-distilled water, methanol, toluene and aqueous NaCl solutions. An empiric equation of state for fitting of the (p,rho,T) data of [EMIM][NTf(2)] has been developed as a function of pressure and temperature. This equation was used for the calculation of the thermal properties of IL, such as isothermal compressibility, isobaric thermal expansibility, differences in isobaric and isochoric heat capacities, thermal pressure coefficient, and internal pressure.