Testicular cancer is the most common cancer diagnosed in people aged between 15 and 39 in Western countries, however it can occur at any age. Most people diagnosed with testicular cancer will have cancer confined to the testicle, without evidence of spread to other areas of the body. These men are highly likely to fully recover following surgical removal of the testicle (orchidectomy) alone, and most will not require additional chemotherapy or radiotherapy. Sometimes, a person may choose to undergo preventive chemotherapy or radiotherapy, which reduces the risk of their cancer coming back; however, this may result in long-term side effects for some people. For this reason, most people in Australia are recommended “active surveillance,” which involves regular reviews with their doctor, computerised tomography (CT) scans and blood tests, but no chemotherapy or radiotherapy. With this approach, most people will be spared from unnecessary treatment and side effects. However, a small number of these people will have recurrent cancer detected during active surveillance. Reassuringly, these people are also highly likely to have a positive outcome following additional treatment. A new blood test, micro-ribonucleic acid (miRNA), which evaluates a protein commonly found in testicular cancer is under investigation. Early studies have found that miRNA is detectable in blood samples of people who have known testicular cancer.