This study developed a mathematical model of human cardiopulmonary system which consists of component models such as ventricular mechanics, hemodynamics of the systemic and pulmonic circulations, baroreflex control of arterial pressure, airway/lung mechanics and gas transport. Instantaneous elastance functions were used to describe the mechanics of the heart chambers. The resistive, compliant and inertial properties of the circulatory system were characterized by a lumped equivalent hydraulic circuit. Transfer functions were employed to represent the input-output relations of baroreflex pathways. On the pulmonary side, the airways were characterized using a lumped pneumatic model containing a mid-airway collapsible segment. Description of lung mechanics included the resistive, compliant properties of the lung tissue, which exhibited hysteresis. Gas transport was characterized by a distributed compartmental system containing ten contiguous segments. With suitable parameter adjustment, the nominal case simulation yielded realistic predictions of pressure, volume and flow waveforms that agreed well with published data. In addition, it predicted the temporal behavior of variables that are not routinely collected in cardiac catheterization or pulmonary laboratories, and which are difficult to measure. The model also demonstrated stability under large amplitude perturbations of the physiological variables, such as Valsalva maneuver. This model maybe employed usefully to show the detailed nature of normal human cardiopulmonary interactions and baroreflex control (e.g. ventricular interaction, Valsalva maneuver). It also provides methodologies for the development of more specific models of abnormal behavior, and as such, may serve as an aid in clinical diagnosis.