In this paper, the results will be presented of an experimental investigation on the overall effects of trace quantities of hydrogen sulphide (H2S) in hydrogen on the performance of a single molten carbonate fuel cell. Involving two primary research centres in Italy and South Korea, the campaign is being carried out with the objective to establish the boundary conditions for durable MCFC operation in the presence of a key contaminant like H2S, in view of extending this knowledge to operation of a MCFC stack on biogas from anaerobic digestion. To achieve this, many hours of long-term experimentation are required and the collaboration of ENEA and KIST aims to make critical mass in this respect. Before looking at the combined effect of H2S in biogas, an experimental survey is carried out of the occurring mechanisms in synthetic, laboratory gas (hydrogen and carbon dioxide) and the possibilities for measurement and diagnostics. The extremely limited quantities of H2S involved combined with the multitude of correlated effects make correct assessment of the mechanisms and the fate of H2S in an MCFC extremely difficult, so that several measurements techniques have been applied. The results obtained from the two laboratories are compared and analysed for future conversion into a schematic model of poisoning conditions.