The effect of the fixatives: 10% formol saline, Carnoy's fluid, Zenker's fluid, Helly's fluid and Bouin's fluid on the staining ability of the extracts of Pterocarpus osun (P. osun) on tissue sections was studied. Tissues were fixed in the fixatives, processed by the paraffin wax method and the sections were stained with alcoholic extract of P. osun in acidic, neutral and alkaline media. No significant difference was observed in the staining reactions