A large proportion of the maize genome is repetitive DNA (60-80%) with retrotransposons contributing significantly to the repetitive DNA component. The majority of retrotransposon DNA is located in intergenic regions and is organized in a nested fashion. Analysis of an 8.2-kb segment of maize genomic DNA demonstrated the presence of three retrotransposons of different reiteration classes in addition to lactate dehydrogenase and pyruvate decarboxylase pseudogenes. Both of the pseudogenes were located within a defective retrotransposon element (LP-like element) which possessed identical long terminal repeats (LTRs) with inverted repeats at each end, a primer binding site, a polypurine tract, and generated a 5-bp target site duplication. A model describing the events leading to the formation of the LP-like element is proposed.