The chromosome 9p21 (Chr9p21) locus was discovered in 2007 by independent genome-wide association studies for coronary artery disease. Since then, the locus has been replicated numerous times and can be considered the most robust genetic marker of coronary artery disease today. Subsequent work has shown associations of Chr9p21 with a number of additional cardiovascular disease traits, such as carotid artery plaque, stroke, aneurysms, peripheral artery disease, heart failure, and cardiovascular mortality, suggesting a more general role in vascular pathology. Importantly, Chr9p21 lacks associations with common cardiovascular risk factors, such as lipids and hypertension, indicating that the locus exerts its effect through a completely novel mechanism. One of the challenges is that the core haplotype block at Chr9p21 resides in a region of the genome devoid of protein-coding genes. Recent progress has been made by functional studies focusing on differential expression of antisense noncoding RNA in the INK4 locus (ANRIL), which is transcribed from the Chr9p21 locus, as well as neighboring protein-coding genes at the INK4/ARF locus. The emerging concept suggests that ANRIL might constitute a regulator of epigenetic modification and thus modulate cardiovascular risk. Here, we review the current clinical, mechanistic, and diagnostic implications of the Chr9p21 locus in cardiovascular disease.