Some believe that the incidence of spoilage microorganisms in wines has increased in recent years. Though not all winemakers agree with this speculation, two issues of potential importance are increases in must pH and a wider application of improved detection methods. Winemakers have experimented with delaying fruit harvest as a means to favorably alter flavor and tannin profiles. In many cases, wine quality has improved. However, one consequence of this practice is that grapes frequently suffer from higher pH, a condition favorable to the growth of various microorganisms (Davis et al., 1986a). The pH of musts also influences the effectiveness of SO2 with less amounts of the antimicrobial portion (molecular) present at higher pH. As such, some have suggested that the increased “hang-time” prior to harvest can also adversely impact wine quality by encouraging the potential for microbial spoilage. Another issue has been application of improved methods to detect microorganisms in musts and wines. Perhaps the most important are the so-called “real-time” molecular techniques. Based upon determination of similarities at the gene level, these methods are being used to identify and, in some cases, quantify microbiological populations. While these methods offer tremendous opportunities to improve microbiological control during vinification, there are potential limitations to routinely using these methods in wine analysis. This paper summarizes the impact of selected spoilage microorganisms, namely Brettanomyces, Pediococcus, and Lactobacillus, on wine quality as well as some methods for detection.