This study aims to evaluate oxidative stress status and investigate some important genes that were related to type 2 diabetes mellitus. This study was a case-control study conducted from November 2015 to April 2016 and included 60 Iraqi patients with diabetes mellitus type 2 (35 females and 25 males) with an average age (40-60 year), and it was carried out at diabetes and endocrine care center Al-Sadder Teaching Hospital, Al-Najaf, Iraq. Also, this study included 40 of apparently healthy people who were (20 females and 20 males) with an average age (40-60) as control matched with disease groups. The present study was divided into two main parts: biochemical and molecular. The biochemical part included study total antioxidants status (TAS), reactive oxygen species (ROS) levels and fasting blood glucose (FBG) levels, while molecular part included study catalase gene by using polymerase chain reaction technique (PCR) and restriction fragment length polymerase (RFLP-PCR), and GSTM1 and GSTT1 genes by using Multiplex technique.