There are a few similarities between the gmat and GRE, they are both computer adaptive and the quant sections are very similar (except the GRE quant is supposed to be easier). The quant section on the GRE is split into two 35 minute sections where the quant section on the GMAT is one 75 minute section. With the GRE, you have to write two essays and the GMAT you only have to write one. The GRE you also have an experimental section that could be quant or verbal. On the GMAT, they integrate experimental questions into the exam. THE GRE also tests vocabulary, where the GMAT does not.