Summary— Sixteen thousand, seven hundred and ninety-six men underwent vasectomy between 1970 and December 1983 and have been reviewed. Post-operative side effects were few and significant complications were reported in 0.9%. Failure to achieve sterility occurred in 72 men, 69 of whom have been analysed. The early recanalisation rate was 0.36%. This rate was not influenced by the operative technique used, but varied markedly between individual surgeons. Experience and care with technique should result in a failure rate of 0.2% or better. There were six cases of late recanalisation in men previously thought sterile by two consecutive azoospermic analyses 4 months after vasectomy.