Moloney Murine Leukemia Virus Reverse Transcriptase, RNase H Minus (M-MLV RT [H-]), is an RNA-dependent DNA polymerase that can be used in cDNA synthesis with long messenger RNA templates (>5kb). This form of M-MLV Reverse Transcriptase has been genetically altered to remove the associated RNase H activity. Although many researchers are successful in using M-MLV RT (H+) for analytical and some preparative cDNA applications, reverse transcriptases lacking RNase H activity provide another option to prepare long cDNAs and libraries containing a high percentage of full-length cDNA.