This work aims to study the effect of residual stresses created by quenching processes on the fatigue behavior of low carbon steel .The quenching was achieved from a temperature of (900 °C) using water or oil as quenching medium. Quenching from a temperature of (850 °C) in oil was also used to produce dual phase steel. The specimens were divided into two groups, the first was subjected to tempering for (1 hr) at (200 °C) after quenching, and the second was without tempering. The results showed that the specimen which was quenched in water and tempered has the highest value of fatigue limit (356 MPa), and the specimen which was quenched in oil from (850 °C) and tempered showed a lower fatigue limit.