Episiotomy is an obstetrical procedure which extends the vaginal vestibule during fetal expulsion. Lateral episiotomy is widely used, but is rarely mentioned in the literature and its effect on the pelvic floor is unexplored. The available data largely support the theory of the negative or neutral effect of median and mediolateral episiotomy on the pelvic floor. The hypothesis of this study was that lateral episiotomy in primiparas has a protective effect on the emergence of urinary and anal incontinence, as well as sexual dysfunction during the first year postpartum. The aim of this study was to investigate the effect of lateral episiotomy on the pelvic floor in the primiparas in comparison to the group without episiotomy. Prospective study was conducted and consisted of 2 groups, with 100 examinees in each group. The first group consisted of women who had a delivery with lateral episiotomy and another group of women who had a delivery with perineal tears of I. and II. degree and intact perineum. The study included primiparas with singleton pregnancies and spontaneous onset of labor with fetuses in cephalic presentation. Examinations of pelvic floor were conducted at 5 and 8 months after delivery accompanied by specific questionnaires. International Consultation on Incontinence Questionnaire-Urinary Incontinence-Short Form was used to assess urinary incontinence, while Wexner Scale was used to assess anal incontinence. Female Sexual Function Index was used to assess sexual function. The clinical examinations were consisted of: Pelvic Organ Prolapse Quantification system, cough stress test, transperineal sonography of anal sphincter and pelvic floor muscles and vaginal manometry. There were no significant differences in emergence of stress urinary incontinence between groups in two-time points (episiotomy: 16% and 13.5%; ruptures: 20% and 14.9%). There were also no differences in the occurrence of prolapse. Pelvic floor muscle strength was almost equal by groups as well as the occurrence of symptoms of anal incontinence and sexual dysfunction. There were certain relations between the ages of the examinees, oxytocin and weight of the newborn to poorer results of the questionnaires in episiotomy group. Obstetric and anthropometric variables were not associated with emergence of urinary and anal incontinence in episiotomy group. Our results indicate that the effect of lateral episiotomy on the pelvic floor is comparable to delivery with minimal perineal injuries. Rates of pelvic floor disorders as well as sexual dysfunction were similar by groups. No substantial associations between episiotomy and pelvic floor disorders have been found which is in accordance with majority of studies on other types of episiotomy. To conclude, lateral episiotomy has neither protective, nor negative effect on the onset of pelvic floor disorders and sexual dysfunction in the primiparas.