6-Methylsalicylic acid is a core salicylic acid unit in the biosynthesis of many secondary metabolites in actinomycetes, fungi and lichens. Reports of its isolation date back to 1917 when it was noted as a precursor of epoxydon biosynthesis. 6-Methylsalicylic acid is an important polar co-metabolite present in many fungi, notably Trichomonacea, and in lichens. 6-Methylsalicylic acid is a useful standard for bioassay and analytical techniques for dereplication of common co-metabolites.