Ole e 1 is a major allergen from olive pollen with an IgE-binding frequency around 80% among allergic population. Its diagnostic value has been demonstrated, and cross-reactive allergens have been found in ash, lilac and privet. We sought to determine IgE- and IgG-binding regions of Ole e 1. Ole e 1-specific polyclonal antiserum and sera from patients allergic to olive pollen were used to analyze IgG and IgE epitopes, respectively. Short overlapping synthetic peptides covering the complete sequence of Ole e 1 and point mutants of these peptides bound to membranes, as well as long recombinant peptides fused to GST were used in dot blot immunostaining and ELISA. Skin prick tests were performed on 14 allergic patients to assay the response in vivo to the recombinant fusion peptides. Residues at positions 8-11, 29, 32, 33, 55-59, 70, 107-110, 112, 120, 123, 141 of Ole e 1 sequence were found to be antigenically relevant in the IgG-binding. Although amino acids K137, L138, G139, Y141 and P142 were involved in the IgE-recognition of a pool of sera from allergic individuals, the response to the IgEs seemed to be preferentially conformational. IgE-binding capability of recombinant GST-fused peptide T114-M145 was demonstrated by in vivo (prick test) and in vitro (ELISA) experiments. Major IgG and IgE-binding regions of Ole e 1 have been identified being the C-terminal an immunodominant region. These data could help to design hypoallergenic forms of the allergen.