Laparoscopic complications are most often related to insertion of the Veress cannula or primary trocar. We evaluated the midline abdominal walls of 33 women using magnetic resonance imaging (MRI) or computed tomography to determine if the location and angle of placement of the Veress cannula and primary trocar should be chosen according to the patient's weight to minimize the risk of both preperitoneal placement and retroperitoneal vessel injury. The anterior abdominal wall thickness was measured for three standard approaches used for placement of laparoscopic instruments through the umbilicus at both 45 degrees and 90 degrees from the horizontal. In addition, the distance from the base of the umbilicus to the retroperitoneal vessels was measured. We found that in the nonobese patient, both the Veress cannula and primary trocar can be inserted at 45 degrees, at either the lower margin or base of the umbilicus, with little risk of preperitoneal placement or major vessel injury. In the overweight patient the cannula and trocar can still be inserted at 45 degrees, but placement through the base of the umbilicus rather than the lower margin will minimize the chance of preperitoneal placement. In the majority of obese patients it is only by placing both the Veress cannula and sharp trocar through the base of the umbilicus at or near 90 degrees that preperitoneal placement can be avoided. Alternatively, an open laparoscopic technique can be considered in such high-risk patients to decrease the risk of major vessel injury.