This retrospective study examined the effect of hysteroscopic correction of an incomplete uterine septum on IVF outcome. Measurement of the Fm (fundal myometrial thickness) and Cm (cornual myometrial thickness) was performed by sonohysterography. Group 1 included patients diagnosed with incomplete septum (n = 119), fulfilling the two criteria of Fm >11 mm and Fm-Cm >5 mm, who underwent hysteroscopic incision of the incomplete septum. Group 2 consisted of 116 age-matched control patients with a normal uterine cavity who underwent IVF within the same time period. Main outcome measures were clinical pregnancy and spontaneous abortion rates. Patients in group 1 had a history of more spontaneous abortions than patients in group 2 (14.20 versus 6.03%, P = 0.04) as well as higher previous IVF failure (32.7 versus 20.6%, P = 0.04). After surgical correction of the septum in group 1, IVF pregnancy outcome was similar in both groups (clinical pregnancy and pregnancy loss of 47.80 versus 46.50% and 10.52 versus 20.3% respectively). A similar pregnancy outcome was found after the incision of the incomplete septum compared with a group with normal uterine cavity. Larger prospective and randomized controlled studies are needed to prove the positive effect of correction of an incomplete uterine septum on IVF outcome.