Precursors for use in metal organic vapour phase epitaxy (MOVPE) of compound semiconductor films are supplied in high integrity stainless steel containers to ensure the highest levels of purity and safety are maintained. However, this means that an accurate level determination is difficult to obtain in situ and growers must rely on usage calculations based on source vapour pressure values quoted in the literature. A number of level sensing systems have been investigated with some degree of success to address this problem, but all have suffered from excessive complexity, being limited to a fixed level indication, fragility and other issues. The most suited technology has been identified as capacitance related and data is reported here obtained from a simple, compact, robust probe fitted to a standard MOVPE bubbler. Results from standard source materials trimethylaluminium (TMA), trimethylgallium (TMG), dimethylzinc (DMZ) and diethylzinc (DEZ) under static and simulated chemical vapour deposition (CVD) operating conditions reported here clearly demonstrate that an accurate continuous level can be measured. Information on the repeatability, material compatibility and temperature dependence of the probe is also presented. (C) 2003 Elsevier B.V. All rights reserved.