The postantibiotic effect (PAE) is defined as the persistent growth suppression of bacteria after exposure to an antimicrobial agent for a limited period of time. Postantibiotic growth suppression is a feature of a variety of antibiotics, although qualitative and quantitative differences were found when a great number of drug-organism combinations were investigated in vitro. Recent research on PAE indicates that effects of clinical interest may be more than just persistent inhibition of bacterial growth. This review focuses on new aspects of the PAE, newer methodology for determination and quantitation, co-factors and possible role for optimizing dosage schedules in antimicrobial chemotherapy. A major future contribution would be the assessment of virulence factors and bacterial toxicity in the postantibiotic phase of microorganisms primed by different classes of antibiotics.