There are several possibilities: Check the integrity of the RNA by denaturing agarose gel electrophoresis (2). RNA should have a minimum A260/A280 ratio of 1.7 or higher. Ethanol precipitation followed by a 70% ethanol wash can remove most contaminants such as EDTA and guanidinium. Precipitation with lithium chloride can remove polysaccharides (2). Phenol/chloroform extraction and ethanol extraction can remove contaminant proteins such as proteases (2). Some target RNA may contain strong pauses for RT; Use random priming instead of d(T)23VN. Use sufficient amount of RNA.