In this article 11 ashes from various Turkish lignite sources were studied to show the effects upon lignite ash quality for use as a mineral admixture in concrete. The lignite ashes were classified into two general types (Class A and Class B) based on total of silica, alumina, and iron oxide. Total content of the three major oxides must be more than 50 % for Class A lignite ash and more than 70 % for Class B lignite ash. When 25 % of the cement was replaced by LA-1 (Class A) lignite ash, based on 300 kg/m(3) cementitious material, the 28-day compressive strength increased 24.3 % compared to the control mix. The optimal lignite ash replacement was 25 % at 300 kg/m(3) cementitious material.