This study describes our experience with seed loss and retrieval through the urinary tract following seed implants for prostate cancer, and offers Japanese guidelines for safety and management. Two hundred consecutive patients were analyzed. All patients were preplanned with a modified peripheral loading technique and implanted with a Mick applicator under ultrasound guidance. All patients were instructed to return excreted seeds, if any, to our center. Seed loss occurred in 6% of patients and 0.13% of seeds. Seed loss tended to occur in the early period through either urine or ejaculation.