B AC K G R O U N D The aim of this study to determine frequency of carriers for β thalassemia and sickle cell trait in the people who applied to the Mersin P r o f . D r . Muzaffer Aksoy Diagnosis Center for the Genetic Blood Diseases. M ET H O D S People who applied to Mersin center station and the stations at the seven districts in between 2nd February 1999 and 1st February 2000 were included in the study. The complete blood count and the haemoglobin electrophoresis were performed in all applicants. R E S U LT S The study were included 12.173 people of those 50% were male and 50% were female. It was found that 2.3% of the participants are the carriers of β thalassemia, 1.3% are the carriers of the sickle cell trait. There were not significant relationship between the disease frequencies and the sexes. CO N C L U S I O N S A cc o rding to the data of the Ministry of Health, β thalass em ia carrying rate of the healthy pop ul at ion of Turkey is 2.1%. The prem ar ital screening tests are the imp o rt a n t protect ive health serv ices in det e rm ining the carr iers and a v o iding the births of the carr ier or sick children. With the help of the prem ar ital screening program performing in Mersin, it is exp e cted that the haemogl ob in opathy freq uency will red uce throughout the foll owing years.