Considerable interest has emerged over the last decade regarding the role of 
aspirin in prevention of colorectal cancer. This disease is one of the commonest 
cancers in the Western World, therefore, the existence of a simple "everyday" 
agent, which could have the ability to prevent the disease, represents an 
invaluable opportunity clinicians may be able to exploit. Evidence from 
case-control and cohort studies, and recent updates of randomised controlled 
trials have been very encouraging-indicating benefit from long term use of 
aspirin at low dose. Possible mechanisms of chemoprevention include inhibition 
of the cyclooxygenase (COX) pathway, or COX-independent mechanisms, for example, 
the PIK3CA pathway, or therapy-induced senescence of cancer cells. The most 
serious side effect of prolonged aspirin treatment is haemorrhage, especially 
from the GI tract. This is likely to be less of a problem with chemoprevention 
at lower doses. One also needs to consider the impact if aspirin resistance, an 
increasingly recognised clinical entity.