Heart cells in culture need no external stimulation to contract; they beat rhythmically at a rate and intensity dependent on culture conditions. These cells respond to the general anesthetic 2-bromo-2-chloro-1,1,1-trifluorethane (halothane), with a loss of beating intensity and a lessening of beating rate. Increased calcium concentrations in growth medium reversed the halothane-depressed beating intensity of heart cells in culture; however, increased calcium concentrations had no effect on the halothane-depressed beating rate. Calcium uptake and release took place in two phases, fast and slow. Only the fast calcium uptake was affected by halothane. Like halothane-depressed beating intensity, the halothane-depressed fast calcium uptake also can be reversed by increased calcium in the growth medium of beating heart cells in culture. Data in this manuscript support the theory that general anesthetics dissolve in membranes and thus disrupt membrane function. The anesthetic halothane appears to affect myocardial beating intensity through its ability to disrupt fast calcium uptake. Halothane also depresses the cardiac beating rate, but the data collected do not relate beating rate with calcium metabolism.