The Buccal Micronucleus Cytome (BMCyt) assay is a new minimally invasive system for studying DNA damage, chromosomal instability, cell death, and the regenerative potential of buccal mucosal tissue. This method is increasingly being used in molecular epidemiologic studies investigating the impact of nutrition, life-style factors, genotoxin exposure, and genotype on DNA damage and cell death. Biomarkers of this assay have been associated with increased risk for accelerated aging, cancer, and neurodegenerative diseases. This protocol describes the current established methods for buccal cell collection, slide preparation, cellular and nuclear staining, and scoring criteria.