Aspirin may protect women from the most dangerous form of skin cancer, research has shown.
The longer a woman takes the painkiller, the lower the risk of melanoma, scientists discovered.
Researchers in the US observed women aged 50 to 79 for an average of 12 years and recorded any cases of cancer.
The women were questioned about what medications they took as well as their diet and lifestyle.
Data from 59,806 women showed that those who took more aspirin were less likely to develop melanoma skin cancer.
Overall, aspirin users were 21% less at risk than non-users.
Each step-rise in the duration of aspirin use was associated with a greater degree of protection.
Women who had regularly been taking aspirin for five or more years were 30% less likely to develop melanoma than women who did not use aspirin.
The scientists controlled for differences in skin pigmentation, tanning practices, sunscreen use, and other factors that might affect the risk of skin cancer.
"Aspirin works by reducing inflammation and this may be why using aspirin may lower your risk of developing melanoma," said study leader Dr Jean Tang, from Stanford University School of Medicine in the US.
The findings are published in an early online edition of the journal Cancer.
Other pain-killing medicines, such as paracetamol, did not lower melanoma risk, said Dr Tang.
The results justified a bigger clinical trial to see whether aspirin can be taken to prevent the disease, she added.
The research formed part of the Women's Health Initiative, a major US investigation into links between lifestyle and disease.
Each year around 13,000 people are diagnosed with malignant melanoma in the UK and 2,200 die from the disease.