The quinolone class of antibacterial agents has evolved rapidly to emerge as one of the most effective classes of drugs in the treatment of infectious diseases. While the spectra and antibacterial activities of fluoroquinolones, such as ciprofloxacin, developed in the 1980s improved to include most gramnegative bacteria, their activities against gram-positive bacteria remained limited. However, the 1990s have seen the synthesis and development of several agents such as sparfloxacin and clinafloxacin (PD127391, C1960, and AM-1091) with good activities for gram-positive bacteria (see Table 1). This article reviews the mechanism of action of quinolones for grampositive bacteria and the mechanisms of resistance by which these organisms evade quinolone action. It focuses on four groups of bacteria: the staphylococci (about which most of the data have been published), the enterococci, the streptococci, and anaerobic gram-positive bacteria.