AbstractWe describe the method and application of a reliable thionin Feulgen stain for paraffin sections of formalin fixed, routinely processed surgical pathology specimens. The technique substitutes thionin for basic fuchsin in the classical Schiff reagent and modifies the hydrolysis times. Serial sections cut from selected paraffin blocks were processed with both a commercial kit stain and the thionin Feulgen stain. Computer assisted image analysis was used to perform a direct comparison of tissue response to the two stains. The thionin Feulgen reagent yielded results as reliable as those from the commercial kit stain, at approximately one-fifth the cost. (The J Histotechnol16:113, 1993)