The goal of this study was to identify the cells from the rat tracheal epithelium which attach and proliferate in primary culture. When cells isolated from tracheas by enzymatic digestion were held in suspension at 37 degrees C for several hours most of the differentiated cells died. The kinetics of this selective cell death were not dependent on the constituents of the holding medium. With time in suspension, the colony forming efficiency of the surviving cells increased two- to threefold. Comparison of the growth curves of cells held or plated directly showed no difference in the number of cells in the proliferating populations. Using two lectins, it was possible to monitor the loss of specific populations in suspension. BS1-B4 is a marker for basal cells and UEA-1 is a secretory cell marker. Only those cells that were BS1-B4 positive survived in suspension. Further, the colonies that formed in primary culture were positive for this marker. Single cell suspensions of cells were sorted by flow cytometry and a fivefold increase in the colony forming efficiency of BS1-B4 positive cells compared to that of the negative cells was observed. These findings suggest that the cells that survived in suspension and proliferated in culture originated from the basal cells of the trachea.