A simple and rapid PCR method was adapted to DNA analysis of cereal seeds. Half-seeds of rice, wheat, and maize were treated with an extraction buffer and the resulting supernatants were used in PCR and RAPD reactions. PCR products amplified from the half-seed DNA extracts were identical with that from leaf tissue DNA extracts when the same specific primers were used in PCR reactions. The remaining half-seeds with embryos could still germinate normally. The half-seed PCR analysis was applied to the identification of resistant genotypes of rice bacterial blight, and it was proved effective in plant breeding and genetic studies.