ABSTRACT. We observed 3 types of non-parental banding patterns using simple-sequence repeat primers in a recombinant inbred line maize population developed from 2 inbred lines, Mo17 and KW7. We observed alleles that were not present in either of the parents, known as non-parental alleles. Although non-parental alleles are a consequence of genetic variation, they are less common in progenies derived from inbred lines. Generally, when non-parental alleles are encountered during genotyping analysis, they are either deleted from the analysis or considered to be missing data. However, before making a decision regarding how to treat non-parental alleles, it is important to understand the mechanism through which they form. There are a variety of potential reasons for the formation of non-parental bands, including recombination or mutation in the simple-sequence repeat region, residual heterozygosity in parental lines, or chromosomal aberrations resulting from rearrangements and transposons. In this article, we discuss the potential reasons behind the formation of the non-parental alleles observed in our data.