We developed a two-compartment model to simulate neuromuscular function and heart rate following the administration of four nondepolarizing neuromuscular blocking agents (atracurium, vecuronium, pancuronium, and d-tubocurarine), three neuromuscular block reversal agents (edrophonium, neostigmine, and pyridostigmine), and two anticholinergic agents (atropine and glycopyrrolate). Twitch depression, train-of-four ratio, and heart rate were modeled during fentanyl, halothane, enflurane, or isoflurane anesthesia, optionally supplemented with nitrous oxide. Simulation results, compared with published values for each drug, fell within the clinical accuracy range (onset time 6.1 +/- 3.9% [mean +/- SEM]; duration, 1.7 +/- 3.5%, 50% effective dose, 0.5 +/- 5.7%; and 95% effective dose, 2.1 +/- 1.1%). The simulation graphically demonstrates the pharmacokinetics, pharmacodynamics, and interactions between neuromuscular blocking agents, reversal agents, and anticholinergic agents. During a simulation, the need for frequent monitoring and repeated delivery of a neuromuscular blocking agent to keep neuromuscular blockade stable becomes apparent, especially with the intermediate-acting neuromuscular blocking agents. When inhalational agents are given concomitantly, the task becomes even more difficult, since potentiation changes with anesthetic uptake. Recurarization, tachycardia, or bradycardia may be seen with the simulation if an improper drug regimen is followed. Concurrent simulation of two identical patients allows comparison of different modes of administration, choice of anesthetic agents, and drug doses.