Abstract: The wilt-inducing pathogen Fusarium oxysporum f.sp. lycopersici, a soil borne fungusoccasionally causing considerable yield losses in tomato production, invades the vascular systemand induces characteristic alterations in tomato roots and stems. Arbuscular mycorrhizal fungi(AMF) have been documented for their biocontrol properties; in particular they are well known toimprove the plants nutritional status, mainly phosphorus. We studied the effects of Fusariumoxysporum f.sp. lycopersici and of the AMF Glomus mossae on tomato root morphology.Additionally the plants were treated with a nutrient solution containing different concentrationsof phosphorus. Root length, root surface area (important indicators for water and nutrient uptake)and average root diameter were estimated using the image analysis program WinRHIZO. Ourdata indicate an alteration of these parameters depending on the treatment.