Chromosomal inversion polymorphism has been study in different natural and experimental populations of Drosophila species. D pseudoobscura first studies in Mexico started during the late 30?s of last century, here are shown the relative frequencies of 48 populations in a period of 40 years with a grand total of 7266 third chromosomes analyzed. Globally in those populations a total of 26inversions are present, in most cases their genetic structure is built by five main gene arrangements and three to six in minor frequencies not reaching a particular one more than six percent. This study includes the description of 15new inversions reported else were. The most frequent gene arrangements found were TL, CU, SC, EP and OA thatglobally represent about the 90%of the whole sample. Remaining 21 inversions were found with individual frequencies varying from one to six per cent reaching in general the remaining 10%. In some areas the dominant inversions are CH. AR. ST and PP. in some areas. Important goals of this study are the discovery and description of 15 new gene arrangements as well new species description, D. cuauhtemoci. All of them reported else were.