Men across Northamptonshire will be receiving a free condom in a Valentine's Day card about sexually transmitted infections (STIs).
NHS Northamptonshire has sent out more than 20,000 cards to young men urging them to get tested for STIs.
Men who request and take a free chlamydia test will be sent a pair of pants with "I've been tested" around the waistband.
The cards include a "special poem" and free condom.
Deputy director of public health for NHS Northamptonshire David Spence said: "Our research tells us that young men aged 20 to 24 years are more reluctant than most young people to take a test.
"One in 14 young people who are tested have chlamydia.
"It is easily treated with a course of antibiotics, but if left untreated can cause health problems and possibly infertility."