Problems with reproducible quantification of low abundance targets (<1000 copies) by qPCR. It is a limitation of PCR amplification from small amounts of any complex template due to differences in amplification efficiency between individual templates in an amplifying cDNA population. The Monte Carlo effect is dependent upon template concentration; the lower the abundance of any template, the less likely its true abundance will be reflected in the amplified product. Originally described by Karrer, 1995; see Bustin & Nolan, 2004 for details.