Fourty patients with 32 hydroceles and 11 epididymal cysts were treated by aspiration and instillation of tetracycline. After a follow up period of 24-39 months the cure rate was 77%. Most of the early recurrences were the results of chemical inflammation and vanished spontaneously. This group should therefore not be operated on until three months after their initial treatment. As aspiration of the fluid had allowed palpation of the testis and cytological examination, only a small proportion of patients with recurrences wanted further treatment. We therefore recommend tetracycline sclerotherapy because it is quick, easy, safe, and effective in the long as well as the short term.