Endogenous viral sequences from members of two virus families, the Caulimoviridae and Geminiviridae, have been discovered in several monocotyledonous and dicotyledonous plant species. For the most part, these sequences are replication-defective but those capable of causing infection have been discovered in tobacco (Nicotiana edwardsonii), petunia (Petunia hybrida) and banana and plantain (Musa spp.). Activation of endogenous caulimovirid sequences is one of the major impediments to international banana and plantain breeding efforts. Research on endogen u viral sequences in plants is still in its infancy, with Iittle known about the contributions ofthese sequences to host and virus evolution, nor even a classification system adopted. On a practical note, problems still exist with differentially detecting viral genomic DNA in a host genetic background containing endogenous viral sequences, and a solution to the problem of activation of endogenous viral sequences in banana is still far away. ln this review, answers to some of these questions are sought by drawing on research from the related fields of endogenous retroviruses in animaIs and LTR-retrotransposons in eukaryotes ingeneral.