Aims: Glucan-producing strains of Pediococcus damnosus are considered as spoilage microorganisms because synthesis of glucan leads to an unacceptable viscosity of wine. In this report, we present a polymerase chain reaction (PCR) procedure to detect the presence of such strains in wines. Methods and Results: We developed a direct DNA isolation method from the wine microflora using polyvinylpyrrolidone in order to decrease the polyphenolic concentration. The sequence of the plasmid involved in glucan production allowed the design of a primer pair usable for a specific and sensitive PCR procedure, leading to the amplification of a 563-bp fragment. Conclusions: The detection limit in wine was 10(2) cfu ml(-1). The detection sensitivity could be increased by using a second primer pair in nested PCR assays. Significance and Impact of the Study: The method proved to be efficient for the early and sensitive detection of ropy Ped. damnosus strains during wine-making. Time-consuming culture and colony isolation steps are no longer needed.