A simple Langmuir probe technique has been used to measure the electron density, electron temperature, and plasma potential in the late stages (>5 &mgr;s) of a laser ablated plasma plume. In the plasma, formed following 248 nm laser irradiation of a copper target, in vacuum at a laser fluence of 2.5 J cm−2, electron densities of ∼1018m−3and temperatures of ∼0.5 eV were measured. These values are comparable with those reported previously using Faraday cup detectors and optical emission spectroscopy, respectively. ©1997 American Institute of Physics.