To aid investigation regarding whether a link exists between exposure to tannins in cotton dust and development of byssinosis, high-performance liquid chromatographic (HPLC) methods have been developed and used to examine extracts from cotton dusts and related materials. Use of a C(18) column with a 85/10/5 water/methanol/acetic acid eluent permits examination of the region in which tannins and their phenolic constituents elute. Qualitative and quantitative differences are revealed by such HPLC examination of extracts obtained from (1.) cotton dusts which differ in size (<38 um and 38-75 um); (2) flax dusts derived from materials which were dew retted, water retted, or dew and water retted; and (3) dusts collected on vertical elutriator filters placed in different areas of the work environment. Use of the same HPLC method to examine a Gossypium-derived tannin preparation that showed in vitro mediator-releasing activity and one that displayed no such activity revealed a substance in the active tannin material which was not present in the inactive material.