The desert locust, Schistocerca gregaria (Forskål) (Orthoptera: Acrididae), and the brownspotted locust, Cyrtacanthacris tatarica (Linné) (Orthoptera: Acrididae), were collected from Saudi Arabia to investigate their relationships. Native polyacrylamide gel electrophoreses of five arbitrarily chosen metabolic enzymes extracted from the leg muscles of the two locust taxa were conducted. These enzymes were acid phosphatase (Acph), alcohol dehydrogenase (Adh), β esterase (β est), malic enzyme (Mal) and malate dehydrogenase (Mdh). Twenty presumptive gene loci and 26 polymorphic alleles were recorded. Acph did not discriminate between the two locust species, while the other four isoenzymes discriminated between them. Most of the alleles were monomeric, but Mal and Mdh exhibited dimeric alleles in the samples of C. tatarica. β est fractions were more expressed in C. tatarica, and the three enzymes β est, Mal, and Mdh discriminated clearly between the two species. The similarity coefficient that was calculated according to the number of sharing alleles between the two locusts was found to be 0.69. The isoenzyme variation presented herein seemed to reflect either their physiological adaptation or the taxonomic consequences between the two taxa. Collecting more isoenzymes for more samples could have taxonomic value.