We report eleven new families of MEdium Reiteration frequency (MER) interspersed 
repeats in the genomes of Primates, Rodentia, and Lagomorpha. Two families of 
the human repeats, MER 46 and MER 47, represent non-autonomous DNA transposons. 
These sequences are flanked by TA target site duplications and have terminal 
inverted repeats (TIRs) similar to TIRs of DNA transposons. The sequences of 
five other families of repeats, MER41, MER48, MER50, MER51, and RMER3, resemble 
long terminal repeats of retroviruses. A potential involvement of some of the 
reported MER repeats in the regulation of transcription and genetic 
rearrangements is suggested. Age estimations place the origin of most MER 
repeats at the time of decline in MIR (Mammalian-wide Interspersed Repeats) 
retroposition and before the origin of the Alu family.