Brachytherapy is a type of radiotherapy, or radiation treatment, offered to certain cancer patients. There are two types of brachytherapy: high dose-rate (HDR) and low dose-rate (LDR). LDR brachytherapy is the type that is most commonly used to treat prostate cancer; it may sometimes be referred to as ‘seed implantation’ or it may also be called ‘pinhole surgery’. In LDR brachytherapy, tiny radioactive particles the size of a grain of rice (see Figure 1) are implanted directly into the site of the tumour. These particles are known as ‘seeds’, and they can be inserted linked together as strands, or individually. Because the seeds are inserted or implanted directly into, or very close to, the tumour, they deliver high doses of radiation to the tumour without affecting the normal healthy tissues around it. This means that the procedure is less damaging than conventional radiation therapy, where the radioactive beam is delivered from outside the body and must pass through other tissues before reaching the tumour. LDR prostate brachytherapy (seed implantation) is a proven treatment for early, localised prostate cancer (when the cancer is contained within the prostate). Under a general anaesthetic, the radioactive seeds are injected through fine needles directly into the prostate, so that the radiotherapy can destroy the cancer cells. The seeds are permanently implanted, so they remain in place but gradually become inactive as the radioactivity decays naturally and safely over time.Unlike traditional surgery, LDR brachytherapy requires no incisions and is normally carried out as a day-case procedure. Sometimes a single overnight stay in hospital is required. Patients usually recover quickly from LDR brachytherapy, which means that most men can return to work or normal daily activities within a few days.