© 2017, Turkish Biochemistry Society. All rights reserved.Objective: Macroprolactinemia detection is important to avoid unneccessary tests and overtreatment. High prolactin levels require routine screening and clinicians must be aware of macroprolactinemia frequency encountered with the method in use. In this study we aimed to determine the macroprolactinemia rate in our laboratory. Methods: Prolactin results of different patients analysed on two different immunoassay systems within two consecutive years were evaluated. Analyses were performed on Beckman Coulter UniCel® DxI800 and Roche Cobas® e601 immunoassay systems. Samples for macroprolactin analysis were precipitated using polyethylene glycol (PEG) 6000. Post-PEG recovery < 40% was defined as positive, 40–60% as gray-zone and > 60% as negative for macroprolactin. Results: For the samples analysed on DxI800 (n = 14,958) hyperprolactinemia frequency was 8.1% (n = 1208). One of 138 samples submitted for macroprolactin analysis was positive, while three of them were in the gray-zone. For the samples analysed on Cobas® e601 (n = 14,040) hyperprolactinemia frequency was 13.9% (n = 1954). Eighteen of 238 samples submitted for macroprolactin analysis were positive, while 21 of them were in the gray-zone. Conclusion: A difference was found between two immunoassay systems used in our laboratory in terms of macroprolactinemia rate. However, inability of simultaneous analyses on both systems, lack of evaluation with gel filtration chromatography, and heterophile antibody blocking tube were the limitations.