A novel real-time quantitative PCR (QPCR) assay is described for monitoring CMV DNA load in clinical specimens using the LightCycler. The assay is rapid (< 40 min), easy to carry out, robust, reliable and is capable of detecting from 10 to over 2 x 10(5) CMV DNA copies with a wide linear range. Amplification and detection occur simultaneously, avoiding the need for post-PCR analysis and thereby minimising the risk of carryover contamination. The assay proved to be accurate, specific and reproducible when evaluated in three different laboratories. In addition, LightCycler results were comparable with those of TaqMan, an independent real-time QPCR assay.