This article presents the temporal variation of the ISTTOK plasma density and electron temperature radial profiles determined by a heavy ion beam diagnostic. Pulsed Xe+ and Hg+ primary beams were injected into the tokamak in two similar discharges and Xe2+ and Hg3+ ions were collected by a multiple cell array detector. The ne and Te profiles were determined from the detected currents using an algorithm that takes into account the beam attenuations as well as the ratio between the effective cross sections of the ionization processes Xe+→Xe2+ and Hg+→Hg3+. These profiles were obtained every 1.5 ms along the central 6 cm of the plasma column diameter. The values of the average plasma density and central electron temperature are in good agreement with those achieved by other diagnostics. © 1999 American Institute of Physics.