Isobaric thermal expansivity alpha(p) for a set of highly polar nitrogen compounds was experimentally determined by means of a calorimetric method in the temperature T and pressure p intervals (278.15 to 348 15) K and (5 to 55) MPa. The selected liquids were propionitrile, nitromethane, nitroethane, nitropropane, benzonitrile, and nitrobenzene The experimental results were compared to available literature data, obtaining good results For most of the studied liquids. It was found that the alpha(p) trends against temperature highly depend on the studied pressure: alpha(p) increases at low pressure: however, as pressure is raised, the dependence on T becomes milder, and for some cases, it is obtained that alpha(p) clearly decreases against T at the highest pressures The. results are interpreted based on the phase-transition properties of the compounds, concretely. on vapor pressure and on distance of the experimental pressure and temperature from the critical coordinates