The tomato Cf genes confer resistance to races of the leaf mould fungus Cladosporium fulvum expressing the corresponding avirulence (Avr) genes, in a gene-for-gene manner. The Cf proteins are predicted to be predominantly extracellular membrane bound glycoprotein receptors, which recognise fungal Avr gene products. The Cf-2 protein contains 38 extracellular-type leucine rich repeats, a single potential transmembrane domain and a 37 amino acid tail, predicted to be cytoplasmically located (Dixon et al 1996). Previous studies, on the subcellular location of the Cf proteins, have produced conflicting results. One study using an epitope-tagged version of Cf-9, demonstrated a plasma membrane localisation (Piedras et al., 2000), whilst a second study, using both fusion proteins and epitope-tagging, revealed an endoplasmic reticulum localisation (Benghezal et al., 2000). To resolve the issue of subcellular localisation, 3xc-Myc epitope-tagged versions of Cf-2 under the control of its native promoter and the strong constitutive Cauliflower Mosaic Virus (CaMV) 35S promoter were engineered. These were stably expressed in transgenic tomato and tobacco. The majority of c-Myc:Cf-2 was demonstrated to be found in the plasma membrane and was highly glycosylated. In addition, expression profiling of Cf-2 and Cf-9 was performed using promoter:GUS fusions in transgenic tomato. Both Cf-2 and Cf-9 were developmentally regulated showing little or no expression in very young seedlings, with expression levels increasing dramatically with the emergence of the first true leaves. Cf-9 expression was, also, dramatically induced in true leaves when exposed to crude preparations containing C. fulvum avirulence products.