Aim: Because of advantages and practicability, evacuated gel separator tubes have been used in health care institutes for a long time. In this study we investigated the effects of freezing of evacuated gel separator tubes on routine chemical and immunochemical analyses. Materials and Methods: Blood samples were drawn into two series of tubes for each commercial evacuated gel separator tubes (Vacuette, Greiner and Vacutainer, Becton-Dickinson); after clotting for 30 min at room temperature all the tubes were centrifuged at 1300g for 10 min. Routine biochemical and immunochemical analyses were performed with primary tubes in first serie tubes (Group 1); aliquotes of these sera were stored at -20 °C for 48 hours (Group 2); after centrifugation, the other serial primary tubes were freezed directly at -20 °C for 48 hours (Group 3). Freezed primary and secondary samples were thawed at +4°C and same analyses were performed simultaneously. Results: As the percentage changes of freezed tubes were compared to the initial value of 24 analytes; three analytes in Greiner tubes (uric acid, ALT, and unsaturated iron binding capacity) and five analytes in Vacutainer tubes (uric acid, total bilirubin, HDL cholesterol, ALT and unsaturated iron binding capacity) had a change more than 10%. For immunochemical analyses, only TSH had a change more than %10 in Vacutainer tubes. Conclusions: Storing of freezed blood samples after centrifugation in the evacuated gel separator Greiner and Vacutainer tubes at -20 °C, does not cause significant difference in the results of routine chemical and immunochemical analytes. © TurkJBiochem.com.