Accumulation of proteins related to tobacco PR-la has been compared in pea roots inoculated with either pathogenic (Chalara elegans) or endomycorrhizal (Glomus mosseae) fungi. Furthermore, effects of induction by acetylsalicylic acid (ASA) and chitosan have been studied. Protein related to PR-la was detected by Western blotting in C. elegans-infected roots and, to a much lesser extent, in tissues colonized by the symbiotic fungus. The PR-la related protein was also observed in C. elegans control and chitosan-induced roots, but we could not detect their induction in ASA-treated tissues. PR-Ia RNA transcripts were found in control and C. elegans-infected roots using a cDNA probe in Northern dot analysis. Lower amounts of PR-la transcripts were detected in tissues during endomycorrhizal symbiosis as compared to the pathogenic interaction. A faint signal was also observed in non-mycorrhizal roots.