Diabetes mellitus (DM) is increasing worldwide especially in developing countries. Increasing age, BMI, weight, martial period and family history for diabetes are highly prone to gestational diabetes mellitus. The aim of this work is to estimate prevalence of GDM among pregnant females in Bani-Suef governorate and its hazards on mother and offspring. Our present study was included 1000 pregnant females were followed and their outcomes with estimated gestational age between 24th and 28th week. At first a proforma containing general information was fulfilled, Then the study population were divided into two groups . 1^st group was screened by Random Blood Sugar (RBS) while 2^nd group was screened by a standardized 2h -75 Oral Glucose Tolerance Test (OGTT) according to WHO guidelines of GDM. Our study detected the prevalence of GDM was 2.6%.  There was statistically significance of increasing age and BMI, positive family history of DM and positive history of twin pregnancy. There was no statistically significance as regards history of PCO, past history of GDM and past history of macrocosmic baby. We recommend the early screening before 24th week of gestation, for GDM regardless of any other risk factors and those women with increased BMI, age, weight and positive history of diabetes mellitus has to be considered as high-risk group. All GDM diagnosed women should be closely monitored for glycemic control for good maternal and fetal outcome.