The evolution and inheritance of glyphosate resistance in Palmer amaranth (Amaranthus palmeri) is a major concern for farmers and weed managers.  Previous research has shown resistance to be due to an increased copy number of the 5-enolpyruvylshikimate-3-phosphate synthase (EPSPS) gene through gene amplification, but the stability of this resistance trait is not yet known.  The relative EPSPS copy numbers of F1 offspring were determined by running quantitative PCR (qPCR) reactions on F1 hybrid plants produced from crosses between resistant and susceptible Palmer amaranth.  The twenty crosses included susceptible by resistant, resistant by susceptible, and resistant by resistant, creating twenty F1 populations.  At least ten plants from each of these F1 populations were sampled and tested with qPCR.  Preliminary data have shown a wide spread of copy numbers for the majority of F1 populations (in the general range of 1-80 EPSPS copies), indicating an unstable transmission of copy number, though no F1 copy numbers have exceeded the copy number of the most resistant parent.  One population had very low copy number in all but one individual, suggesting the influence of either apomixis or maternal effects.  However, subsequent genotyping of the F1s and parents of this population ruled out apomixis as a cause of similar copy numbers.  Initial results have also shown a strong correlation between high copy number and level of resistance, as was expected.  More research on the EPSPS gene is needed to confirm these results and to gain an idea about how glyphosate resistance transmission occurs across generations at the molecular level.  It may be that a genetic mobile element with low stability may be partially responsible for the increased EPSPS copy numbers in Palmer amaranth.