Transvaginal ultrasonography, with its higher frequency and proximity to the pelvic structures has offered us a powerful tool for observing the uterine scar of a previous Cesarean section. We have examined 87 previous Cesarean section scars by transvaginal ultrasonography. Forty cases (group A) were in the third trimester. Fifty-two percent of this group showed normal patterns. In the remaining cases, thickening of the previous incision site was the most common finding. Also, thinning, ballooning and wedge defect were noted. Forty-seven cases (group B) were examined within 3 months (group B1) or after 3 months of Cesarean section (group B2). Similarly half of them showed normal patterns. In the remaining cases, wedge defect was the most common finding. The others were outward or inward protrusions, hematoma formation and inward retraction. An evaluation of the previous section scar, preferably by high resolution transvaginal ultrasonography is highly recommended in considering a trial of labor after previous Cesarean deliveries.