Potato virus Y group C isolates (PVYC) have been characterized according to biological, molecular and genetic criteria. Two genetic strains, PVYC1 and PVYC2, were identified on the basis of genetic distances (among them and other PVY strains), host range (ability or inability to infect pepper), MAb response (ELISA recognition with MAb 10E3) and coat protein processing site. Some characteristics, such as aphid transmission and ELISA using other MAbs, did not correlate with classification into these two genetic strains. All isolates tested induced a hypersensitive response on potatoes bearing the Nc resistance gene, confirming the nature of PVYC isolates as a homogeneous pathotype.