Objective: The median values of double test which is commonly used for Down Syndrome screening show diversity between countries. In this study, we aimed to investigate the possible differences in corrected multiplies of median (MoM) values of individiuals between the two cities of the same geographic region. Methods: Blood samples for double test analysis, sent from Corum and Samsun, were studied in the same laboratory. Results of double test analyses were retrospectively evaluated. Mann-Whitney U test was used for comparison of corrected MoM values of free human chorionic gonadotropin (f-β hCG) and pregnancy-specific plasma protein-A (PAPP-A) according to gestational age. Results were given as median (minimum-maximum) values. The p <0.05 was considered significant. Results: The corrected f-β hCG values obtained from Corum and Samsun were as follows: 0.75 (0.24-2.11, n=28), 0.85 (0.21-2.95, n=143) (p=0.378) in 10th gestational week; 0.75 (0.17-4.15, n=349), 0.84 (0.14-4.76, n=672) (p=0.005) in 11th gestational week; 0.81 (0.15-5.15, n=542), 0.86(0.19-5.18, n=946) (p=0.014) in 12th gestational week; 0.77 (0.20-6.32, n=365), 0.87 (0.20-5.54, n=327) (p=0.054) in 13th gestational week, respectively. Corrected PAPP-A values from Qorum and Samsun were as follows: in 10th gestational week 0.94 (0.41-5.57), 0.87(0.19-3.53) (p=0.425); in 11th gestational week 0.88 (0.21-3.61), 0.89 (0.19-3.70) (p=0.963); in 12th gestational week 0.89 (0.22-4.24), 0.90 (0.15-4.99) (p=0.704); in 13th gestational week 0.93 (0.19-2.70), 0.90 (0.09-2.80) (p=0.952) respectively. Conclusion: The MoM values of f-β hCG tests, derived from individuals from Çorum and Samsun, both located in the Central Black Sea Region, were found to be different. This finding indicates that for double test analysis, different median values may be used for patients from different cities.