A pyruvate kinase deficiency prevalence study and determination of the normal levels of the enzyme were performed in Antalya city, Turkey. Heparinized blood samples obtained from a representative population of the Antalya province (617 women and 573 men) were tested for pyruvate kinase deficiency by qualitative and quantitative tests between April 1992 and March 1994. The mean pyruvate kinase activity was found to be 19.8 ± 4.0 IU/g Hb whereas the enzyme activity of deficient cases varied between 7.5 and 12.2 IU/g Hb. Taking into account that pyruvate kinase deficiency is the second most common cause of nonspherocytic congenital hemolytic anemia, detection of deficient cases by genetic screening tests appears to be an informative clinical indicator of hemolytic anemia