Knowing that actin microfilaments play a key role in the mobilization of the defence-associated cellular responses, the aim of this study was to compare changes affecting the actin cytoskeleton in tomato cells after inoculation with germinated microconidia of a biocontrol (Fo47, Fom24) or a pathogenic (Fol8) strain of Fusarium oxysporum. Actin microfilaments were observed by labelling with TRITC-phalloidin combined with fluorescence microscopy. Results showed that only tenuous changes in the actin cytoskeleton architecture occurred after inoculation with the biocontrol strains whereas the actin cytoskeleton was significantly altered after inoculation with the pathogenic one. In the two types of interaction, cell death occurs and can be considered as one key component of cell defence responses. A pharmacological approach using cytochalasins was chosen to determine whether the inhibition of actin polymerization differently affects the kinetics of tomato cell death. Data showed that cytochalasins reduced cell death induced by the biocontrol strain Fo47, and in contrast, increased cell death induced by the pathogenic strain Fol8, suggesting that the pathway leading to cell death differs in the protective and compatible interactions.