Experimental tests cited herein have established that the deposits of inhaled particles may be highly concentrated at carinal ridges within lung bifurcations. The deposition patterns, therefore, have immediate implications to risk assessment programs and aerosol therapy protocols. Herein, the software FIDAP was employed to study the effects of carinal ridge shapes upon fluid dynamics patterns. A series of well-defined geometric shapes (symmetric and asymmetric) were examined. For each case, a wide range of physiologically realistic flows were considered which corresponded to respiratory intensities for sedentary, light, and heavy activities. The results varied in a systematic manner. By relating fluid dynamics patterns to particle behaviors, the results have inhalation toxicology and aerosol therapy relevance because, for example, bronchogenic carcinomas are selectively distributed within the tracheobronchial tree and certain receptors are known to be preferentially located at airway dividing sites.