A survey of the inhibition of the amplification of spinach DNA by various plant polysaccharides revealed that neutral polysaccharides (arabinogalactan, dextran, gum guar, gum locust bean, inulin, mannan, and starch) were not inhibitory. In contrast, the acidic polysaccharides (carrageenan, dextran sulfate, gum ghatti, gum karaya, pectin, and xylan)were inhibitory. In the process of preparing random amplified polymorphic DNAs (RAPDs), the loss of large DNA bands appears to be an indicator that the fingerprint pattern has been affected by polysaccharides. The addition of various concentrations of Tween 20, DMSO, or PEG 400 to the PCR reaction mixture resulted in partial restoration of amplification of RAPDs for the acidic polysaccharides. The most effective way to eliminate the effects of polysaccharide inhibition was by diluting the DNA extracts, and thereby diluting the polysaccharide inhibitors.