The extraction of high-quality DNA is essential for studies conducted at the molecular level in species with an abundance of contaminants in their tissues, such as some landraces of potato and maize, in which it is difficult to extract good-quality genomic DNA. Compounds such as polyphenols interfere with the amplification of DNA during polymerase chain reaction (PCR), which makes it difficult to conduct PCR-based studies ofmolecular markers. This article describes a simple and robust protocol for DNA isolation that was applied to potato and maize landraces and resulted in a high DNA concentration with excellent purity and quality. This method is based on the method of Krizman et al. (2006) with some modifications and was tested on potato leaves and young maize leaves. The protocol was compared with one commercial DNA extraction kit and three methods that were previously described for plant DNA extraction: Keb-Llanes et al. (2002), for plants with high polyphenolic content; Fulton et al. (1995), which was developed for Solanaceae and other herbaceous plants; and the original Krizman et al. (2006) cetyltrimethylammonium bromide (CTAB)-activated charcoal method . The method proposed is suitable for isolating DNA Irom potato and maize genotypes with high polyphenol contents, yielding high-quality DNA that can be utilized for molecular techniques that involve PCR, cutting with restriction enzymes and other applications. The method is short, similar to a commercial kit, but cheaper. The amount of DNA extracted from maize using our method is superior compared with other published methods tested in this article.