We conducted a case matched control study to observe the adverse effects of ciprofloxacin used in neonatal septicemia We enrolled 30 neonates with multidrug-resistant septicemia who were treated with intravenous ciprofloxacin for 14 days. Thirty matched neonates with septicemia treated with other antibiotics were enrolled as controls There was no difference in the mean serum electrolytes, hepatic, renal and hematologic parameters of the two groups. Serial ultrasonographic measurements of the cartilage of the knee after 1 and 6 months showed no difference in the two groups. The femoral cartilage showed an increase of 78.8% in the mean longitudinal area after 6 months in the study group. In the control group, the femoral cartilage showed a 78.4% increase after 6 months. Similarly, the tibial cartilage showed no difference in the percentage increase in size of the study and control group at the end of 6 months. When controlled for birth weight and gestation, cartilage size was not affected by ciprofloxacin.