A recently setup installed around a high pressure electromagnetic viscometer is used for the measurement of dynamic viscosity of selected lactams of the pyrrolidone family. These compounds are widely used in several applications ranging from the petrochemical to pharmaceutical industries. In spite of their importance, no reliable viscosity data are available in the wide pressure – temperature ranges in which they are applied and thus they are reported here by the first time. The accuracy of the apparatus was firstly tested by measuring selected compounds and comparing the experimental data with available reference equations obtaining average deviations below 2% for all the studied systems. Lactams viscosities were measured for temperatures up to 473 K and pressures to 100 MPa. Experimental viscosities were predicted by several available models in order to compare their performance.