Which diamond grading labs are considered to be the best and most accurate?

Within the jewelry industry, the four top respected diamond grading labs are the Gemological Institute of America, The American Gem Society, and the European Gemological Society and Professional Gem Sciences. If you read the fine print of any diamond grading report you will notice that all the labs have disclaimers which state that their reports are not quality guarantees. Diamond lab graders grade diamonds using advanced methods and assess and evaluate their findings which allow them to be subject to human error. Although we can not guarantee qualities, we do check all of our diamonds against their diamond grading reports and reject any that we feel have been graded inaccurately.