Aims: The origin of a mould responsible for the contamination of an Argentinian cheese factory was identi®ed and several antifungal treatments were assessed. Methods and Results: Moulds were isolated and identi®ed from vacuum-packed hard cheeses, from the environment and from the surfaces of the factory. A suspension conidia test containing different fungicides was performed; another assay involved the fumigation with p-OH fenilsalicidamide. Only Phoma glomerata was found in all of the mouldy cheeses, and was also obtained from different environments and machine surfaces. The most effective treatments against P. glomerata isolates were 0á5% (w/v) natamycin and 2% (v/v) parabens. Fumigation with p-OH fenilsalicidamide showed no satisfactory results. Conclusions: P. glomerata is an important thread mould-contaminating agent in vacuumpacked hard cheeses. Signi®cance and Impact of the Study: Taking into account the survival of the conidia of the P. glomerata isolates to different antifungal treatments, the sources of contamination need to be controlled by designing a good factory layout.