The electron field emission characteristics of individual multiwalled carbon nanotubes were investigated by a piezoelectric nanomanipulation system operating inside a scanning electron microscopy chamber. The experimental set-up ensures a precise evaluation of the geometric parameters (multiwalled carbon nanotube length and diameter and anode-cathode separation) of the field emission system. For several multiwalled carbon nanotubes, reproducible and quite stable emission current behaviour was obtained, with a dependence on the applied voltage well described by a series resistance modified Fowler-Nordheim model. A turn-on field of ∼30 V µm(-1) and a field enhancement factor of around 100 at a cathode-anode distance of the order of 1 µm were evaluated. Finally, the effect of selective electron beam irradiation on the nanotube field emission capabilities was extensively investigated.