Establishment of the best combination among heterotic groups, heterotic patterns, is crucial to the development of successful maize (Zea Mays L.) hybrids. The use of molecular markers in maize-breeding programs might or might not increase the efficiency of heterosis prediction by classifying diverse inbred lines into heterotic groups. The objectives of present research were to classify elite North Dakota (ND) maize inbred lines into heterotic groups and evaluate the consistency between simple sequence repeat (SSR) grouping and testcross data. Thirteen ND inbred lines representing diverse genetic background were crossed in a diallel mating design in 2000. The crosses and 12 checks were evaluated across four ND environments in 2001 and 2002. In addition, these lines were crossed to commercial inbred testers representing known heterotic groups in 2002. Hybrids between public and private lines were evaluated across three ND environments in 2003. Inbred lines representing Lancaster Sure Crop, Iowa Stiff Stalk Synthetic (BSSS), Minnesota #13, Northwestern Dent, Golden Glow pedigrees and ND inbred lines were screened with 49 SSR markers. Inbred lines ND246, ND278, ND280, ND281, ND282 and ND284 were clustered within the BSSS heterotic group. Inbreds ND277, ND285, ND286, ND290, and ND291 grouped closer to the Lancaster Sure Crop heterotic group. Inbred lines ND257 and ND288 grouped within Minnesota #13. Data from ND278 and ND290 testcrosses showed good combining ability with testers representing more than one heterotic group. Our research shows that groups of genetically similar germplasm could not be identified accurately and reliably with molecular markers even when the available germplasm was diverse contrary what has been suggested. Therefore, extensive field evaluation is recommended to classify unrelated inbred lines of maize.PUBLICATION ABSTRACT