PURPOSE: The aim of this study was to evaluate the correlations between laboratory findings and ultrasonographic measurements of renal length and cortical thickness in patients receiving follow-up for chronic kidney disease (CKD). METHODS: A total of 41 CKD patients (18 males and 23 females; mean age, 65.2 years; range, 42 to 85 years) with a low glomerular filtration rate who did not require renal replacement therapy were included in this prospective study. Patients were followed up with laboratory assays at bimonthly intervals and with ultrasonography performed twice a year. Renal cortical thickness, renal length, and estimated glomerular filtration rate (eGFR) values were compared using the paired-samples t test. Additionally, Pearson correlation analysis was conducted between renal length and cortical thickness measurements and eGFR values to assess kidney function. RESULTS: At the beginning of the study and after 24 months, mean eGFR values of the 41 patients were 35.92 mL/min and 28.38 mL/min, respectively. The mean renal length was 91.29 mm at the beginning of the study and 90.24 mm at the end of the study. The mean cortical thickness was 5.76±2.05 mm at the beginning of the study and 5.28±1.99 mm at the end of the study. A statistically significant positive association was found between eGFR and mean renal length (r=0.66, P < 0.01) and between eGFR and mean cortical thickness (r=0.85, P < 0.01), with the latter being more prominent. CONCLUSION: Our study suggests that ultrasonographic cortical thickness measurements may be an important imaging technique in the follow-up care of patients with CKD.