The rate of killing of a group A streptococcal species by penicillin was compared with the release of lipoteichoic acid (LTA) and its deacylated derivative, dLTA. Although there was no stimulation of release from stationary-phase cells in the presence of penicillin, there was dramatic release of LTA and dLTA from exponential-phase cells after the addition of penicillin. Although decreases in viability were observed within 15 min after addition of penicillin, culture mass and LTA content did not appear to be affected until after 30 min. Stimulation of release of LTA and dLTA appeared to take place after 15 but before 30 min after addition of penicillin. These observations are interpreted to indicate that the stimulation of release of LTA and dLTA in response to penicillin is secondary to the killing event.