To describe the factors associated with unjustified Cesarean section.Cross-sectional study.Four hospitals providing obstetric services, two that serve patients insured through their employer (contributive regimen) and two that serve privately insured patients, in Cali, Colombia.Four hundred and sixteen patients with Cesarean section performed in 1996 because of previous Cesarean section, dystocia, acute fetal distress, breech presentation and maternal choice. Patients with toxemia, diabetes, hypertension and other related diseases were excluded.Unjustified Cesarean section.Of primary Cesarean sections 81.2% were unjustified. Dystocia was the indication given for unjustified surgeries in 78% of cases. Hospital No. 2 had the highest proportion of unjustified procedures compared to the other three institutions. Patients for whom the procedure had been decided before prelabor and on whom it was performed between 7:00 a.m. and 5:59 p.m. had higher proportions of unjustified procedures.