To obtain monoclonal antibodies (MAB) specific for the different cell types of distal and collecting tubules, BALB/c mice were immunized with cell suspensions highly enriched in cells from the distal segments of the rabbit nephron. Nine MAB were selected and cloned. Four groups could be identified on the basis of double-labeling immunofluorescence (IF) on frozen kidney sections and on microdissected tubules. In addition, binding specificity at the cellular level was studied by immunoelectronmicroscopy (IEM) for selected MAB. A single MAB (group 1) was specific for distal bright cells and a subpopulation of cortical ascending limb cells. Six MAB (group 2) reacted with connecting and collecting tubules. Five of these (group 2A) had similar binding patterns and reacted identically with the two tubular segments. The MAB studied by IEM was specific for connecting and principal cells. One antibody (group 2B) reacted with only a fraction of the cells associated with the connecting tubule (CNT), but with all cells of the cortical collecting tubule (CCT). By IEM, this antibody was found to be specific for intercalated cells in CNT and bound both principal and intercalated cells of the CCT. Two MAB (group 3) reacted with antigen(s) expressed by the various terminal segments of renal tubule. MAB of groups 1 and 2A, which define distal bright cells and connecting-principal cells from the CNT-CCT, respectively, were used for cell fractionation experiments. Heterogeneous rabbit cortical cells were first incubated with the selected MAB. MAB-bearing renal cells were separated on plastic dishes previously coated with an affinity-purified goat anti-mouse immunoglobulin. Using these procedures it was possible to obtain highly purified subpopulations of distal, bright, or connecting-principal cells.