Introduction: The debate over the criteria to screen and diagnose gestational diabetes mellitus (GDM) has been incessant over the last five decades.This study is particularly directed towards evaluating the one-step approach of oral glucose tolerance test (OGTT) versus the two-step process with a screening test of oral glucose challenge test (OGCT) followed by the OGTT as screening and diagnostic criteria in South Indian women. The study also aimed to determine the normal glucose tolerance range in the study population. Materials and Methods: In a study sample of 1200 women, one and two-step diagnostic criteria were applied to 600 women each. After exclusion of those who satisfied the criteria for the diagnosis of GDM, the remaining were evaluated for determination of the normal study population followed by comparative and statistical analysis. We analysed the prevalence of GDM based on more than one abnormal value versus more than two abnormal values. Results: Out of the 600 women subjected to one-step test, 56 (9.33%) were diagnosed with GDM with a sensitivity and specificity of 80.36% and 95.77%, respectively. For the two-step test, 10 (1.67%) were found to have GDM with sensitivity of 90%; and specificity of 66.27% & 53.9 %. Conclusion: Though the one-step screening process is extremely effective, this study has revealed various advantages of the two-step protocol. The prior screening test in the two-step method reduces the burden of testing by oral glucose tolerance test, thereby diminishing laboratory load to a great extent.