The maize breeding program and the Bajío Experimental Station, which belongs to the National Institute of Agriculture, Forestry and Livestock (INIFAP), located in the State of Guanajuato, Mexico, during 1994 and 1995, we evaluated yield trials with four types of genetic material: a. Original inbred lines wich are parents of superior single croses, under the release process. b. Modified parts coming from the cross of the original inbred parent, with a relative inbred line derived from the same germplasm source. c. Theoriginal single cross hybrids, and d. The modifield new crosses from the related parents. The results showed that the modified parents outyield in the original inbred lines, in some cases was of more than 300%. Moreover, some modified hybrids were statistically similar to the original single cross hybrids, as well as in some later commercial checks. The heterotic response, previously identified in specific single hybrids, was kept when we utilized modified parents with high yield. All this supported the idea that this kind of hybrids represent a large potential in the regions where the use of conventional single cross hybrids, is still limited.