Goals: The primary goal of this research was to determin the total amount of the third and fourth degree perineal tears (OASIS, English abbr. obstetric anal sphincter injuries) in the restrictive use of episiotomy. The secondary goal was to determin the frequency of OASIS in comparison to parity, the way a labour was carried out till the end, duration of labour, risk factors for occurence of OASIS, obstetrics teams' experience, birth weight and infant's head circumference within the group of examinees. Factors that have been taken into consideration when analyzing all the information were: rotational and deflection anomalies, shoulder dystocia, registered OASIS in previous labour and non-cooperation of the parturient woman. Materials and methods: Fifty one parturient women were included in this research. They have all given birth in period between January the first 2010 and December the thirty first 2014 at the department of gynecology and obstetrics in clinical centre „ Sveti Duh“. OASIS was diagnosed to them by a specialist examination. Criteria for diagnosis of OASIS were based on Sultan’s classification of obstetrics perineal tears. The data were collected retrospectively going through medical history and labour room protocols. Results: At the time of the research seventy seven percent of women (77%; n=9887) from the total of 12858 vaginal labours did not have an episiotomy while twenty three percent (23%; n=2971) had the aforementioned procedure. The total frequency of OASIS in the research period was 0,4% (n=51). A statistically significant difference was found in the number of OASIS for women who had vaginal labours and a mediolateral episiotomy (0,74%; n=22) when compared to those who gave birth vaginally but without an episiotomy (0,29%; n=29) (p<0,05). The number of parturient women who have had their first child and who were diagnosed with OASIS was 68,7% (n=35) and it was higher than for women who gave birth several times. Within the sub group of women with a mediolateral episiotomy a statistically significant difference was found for number of OASIS among parturient women who gave birth for the first time (57,1%; n=20) and those who gave birth for several times (12,5%;n=2) (p<0,05). A higher frequency of OASIS was found within the group of women who were giving birth for longer than 10 hours and who had an episiotomy (61,1%; n=11) in comparison to women who were also giving birth for longer than ten hours but who did not have an episiotomy (38,9%; n=7) (p<0,05). Thirty three percent of women (33%; n=17) diagnosed with OASIS had risk factors for occurence of OASIS such as (occipito-posterior position, parietal position, deep transverse arrest, shoulder dystocia, previously diagnosed OASIS and non-cooperation of parturient woman). In the mentioned group of 33% of women (n=17), 65% of them (n=11) had their births carried out by the most experienced obstetrics team at the clinic. A statistically significant difference was not found when the infant's birth weight was under 4000g (78,4%; n=40) and above 4000 g (21,6%; n=11) and when the infant's head circumference was less than 34cm (20,8%; n=10) and more than 34cm (79,2%; n=38). Also, a statistically significant difference has not been found when taking into account duration of the second stage of labour for more than 1 hour (43,6%; n=17) or less than 1 hour (56,4%; n=22). Twenty-one point six percent of women had a vacuum extraction (21,6%; n=11) and were diagnosed with OASIS and 78,4% (n=40) spontaneously. Eleven women who have had vacuum extraction 63,6%; (n=7) also had an episiotomy and 36,4% (n=4) did not have one. Forty-three point one percent (43,1%; n=22) of women diagnosed with OASIS had an epidural anaesthesia while 56,9% (n=29) did not have one. Within the group of women who have had epidural anaesthesia 50% (n= 11) were diagnosed with OASIS and had an episiotomy and 50% (n= 11) did not. Conclusion: Frequency of OASIS of 0,4% (n=51) at the department of gynecology and obstetrics in clinical centre „Sveti Duh“ is acceptable because registered frequency of OASIS in literature variess between 0,9% to 4,2%. Frequency of OASIS after mediolateral episiotomy varies from 0,25% to 7% and is registered in literature. Our research records 0,7% frequency of OASIS for women who have had mediolateral episiotomy. Since our research has shown a statistically significant difference in the number of women diagnosed with OASIS with and without episiotomy use, we can conclude that episiotomy use does not prevent genesis of OASIS. Some risk factors such as parity and duration of labour for periods longer than ten hours were singled out as risk factors for occurence of OASIS despite use of episiotomy. One third of the women who were diagnosed with OASIS had risk factors responsible for OASIS. Risk factors for occurence of OASIS were recognised by the obstetrics team before the third or expulsion stage of labour because for more than half of the of the cases the most experienced obstetrics team at the clinic was present at the labour. Infant's birth weight and head circumference, extended duration of second stage of labour for periods of time longer than one hour, surgical intervention in form of vacuum extraction and epidural anaesthesia did not affect the frequency of OASIS.