This study was performed to evaluate the clinical course and renal outcome of patients with unilateral multicystic dysplastic kidney (MCDK). We retrospectively reviewed the medical records of 59 cases with MCDK followed at Şanlıurfa Children's Hospital between January 2009 and February 2013. The median age of the patients (boys 52.5%) was 31 months (range: 6-197) and the median follow-up period was 23 months (range: 6-111). Forty-two (71.2%) patients were diagnosed antenatally. The MCDKs were found more often on the right side (55.9%). The most frequently associated urological abnormality was contralateral vesicoureteral reflux (VUR) (26.6%). A total of 3 (5%) patients developed chronic renal insufficiency (CRI), 2 of whom had grade IV and V VUR; the other patient with CRI had a small and hyperechogenic contralateral kidney, suggesting dysplasia-hypoplasia, without any urological anomalies on imaging studies. The size of MCDK was unchanged in 20 (34%), had regressed in 26 (44%), and had increased in 9 (15.3%) patients. Total involution was documented in 4 (6.7%) patients. Compensatory hypertrophy occurred in 36/45 (80%) patients, with a mean age of 19.2±8.3 months. Proteinuria and hypertension were detected in 1 (1.7 %) patient each. In conclusion, abnormalities in the contralateral kidney in patients with MCDK increase the risk of renal failure. An initial investigation for associated urinary tract malformations should be done and the growth and function of the contralateral kidney, hypertension, and proteinuria should be monitored in all children with MCDK.