Introduction:-Reference intervals are ranges of upper and lower limits outside of which valuesrnwould be considered abnormal. It depends on the type of instrument and reagents, the principlernor method and the type of population being served. Therefore it is obvious that it should bernestablished for every population in different regions even within a country.rnObjective:-The aim of this study is to establish population specific reference intervals of thyroidrnstimulating hormone, free thyroxine and free triidothyronine levels of cord blood.rnMaterials and methodsá¡- A cross sectional study was conducted from July, 2013 to November,rn2013 using cord blood sample from 123 new born infants of both sexes born at Tikur AnbessarnTeaching Specialized Hospital and Gandhi Memorial Hospital. Thyroid stimulating hormone,rnfree thyroxine and free triidothyronine were measured using Elecsys 2010 immunoassayrnanalyzer at Ethiopian Health and Nutrition Research Institute. The non-parametric method ofrnreference range determination was used.rnResults:- 123 Cord blood samples collected from umbilical cord of newborns were analyzed forrnthyroid stimulating hormone, free thyroxine and free triidothyronine values. The birth weightsrnranged between 2500g to 4700g with mean (SD) value of 3241.46(459.495)gram. Theirrngestational age ranged between 37 to 44 weeks with an average of 39.74 weeks. The 2.5th andrn97.5th percentiles ofrnvalues were found to be 3.48 mIU/L and 27.57 mIU/L for thyroidrnstimulating hormone, 0.89 ng/dL and 1.53 ng/dL for free thyroxine and 1.19 pg/mL and 2.51rnpg/mL for free triidothyronine respectively.rnConclusion:- In the present study the reference intervals of thyroid stimulating hormone ,freernthyroxine and free triidothyronine were tried to be established and based on the results obtained ,rnwere 3.48 - 27.56 mIU/L for thyroid stimulating hormone, 0.89 - 1.53 ng/dL for free thyroxinernand 1.19 - 2.51 pg/mL for free triidothyronine. It has been concluded that the result can providernus with an important clue to establish population specific reference intervals using large scalernstudies.rnKey words:-Thyroid function tests, reference intervals, screening program, Congenitalrnhypothyroidism