A study of 38 cases of pregnancy that occurred after sterilisation between 1st January 1981 and the 30th September 1987 at the Maternity and Neonatology Department of La Rabta, Tunis. This complication is rare because the overall global figure for failure is 7.1/1000. This is what is found in the literature. When we came to analyse the failures we found there were two groups: 15% of these failures were in women who had been sterilised correctly. This also happens when women have been sterilised with the Yonn ring as with Pomery's ligation technique. In this case when patients become pregnant there is a big chance of their being ectopic (2 tubal pregnancies as against 5 intrauterine pregnancies). 85% of failures were due to technical faults. They particularly happen with laparoscopic sterilisation (85%). They are usually due to lack of experience on the part of the operator. In any case patients do not like it; in fact 73.7% of the patients asked for a termination of the pregnancy and sterilisation was repeated in 87% of the cases.