Fears have been raised that men are not taking the necessary steps to ensure their vasectomies have been a success.
Researchers suggest a single test may be more efficient
A US study found a quarter of men who had undergone sterilisation did not return for any follow up test to check whether the procedure had worked.
Only a fifth of the 436 men studied at a clinic in Cleveland, Ohio, attended the two sets of sperm-checking tests needed to give them the all-clear.
The study is published in the UK-based BJU International.
Of the 80 men who did attend their first test eight weeks after the operation, three were still producing active sperm.
One of these was later diagnosed with a vasectomy failure.
Dr Nivedita Dhar, chief resident urologist at the Glickman Urological Institute where the study was conducted, said: "Our results show that only three quarters of the men in the study turned up for their eight-week sperm test.
"This means a quarter of them had no idea whether the procedure had worked and whether their partner could still fall pregnant."
She added: "It is impossible to assess the true vasectomy failure rate in the full study sample as many failed to turn up for follow-up tests, despite careful counselling."
Vice-chairman of the institute Dr J Stephen Jones who directed the study said the other research suggested the non-compliance with follow-up checks among vasectomy patients was between 25 and 40%.
"It may, however, be possible to improve full compliance among those who return for at least one test by simplifying the follow-up tests in line with current medical evidence and making sure that this is backed up by adequate counselling."
He pointed out that the study had shown 65 men tested at eight weeks needed re-testing, but at 12 weeks only 15 needed retesting.
"This suggests that a single test at 12 weeks may be adequate in the majority of cases.
"However, it is very important to stress that couples need to use additional contraception until the vasectomy patient has been given the all clear," Dr Stephen Jones added.
Secretary of the British Fertility Society and Senior Lecturer at the University of Sheffield Dr Allan Pacey said it was obviously very important for men to return for semen analysis to check whether or not their vasectomy surgery has worked.
"It is also vital that the laboratory undertaking the analysis of the sample does it properly.
"Diagnosing whether there is sperm in the ejaculate is quite tricky to do and in the UK we have strict guidelines that all laboratories should adhere to.
"But it does not matter how strict they are if the man does not turn up for testing in the first place!"