Patients with previous cesarean births who delivered macrosomic infants (greater than or equal to 4,000 gm) during the study periods January 1 to December 31, 1980, and July 1, 1982, to June 30, 1983, were analyzed to determine the impact of fetal weight on a trial of labor (TOL). Of 140 women with macrosomic infants given a TOL, 94 (67%) delivered vaginally. The most common indication for cesarean delivery was cephalopelvic disproportion (CPD). The dehiscence rates were similar when patients who underwent a TOL were compared with those who did not. Factors associated with a successful TOL were a previous vaginal delivery after the original cesarean section, no oxytocin usage during the TOL and an indication for the previous cesarean section other than CPD. The risk associated with a TOL in a patient with a previous cesarean birth and a macrosomic infant appears to be no greater than that encountered in a similar group of patients without uterine scars.