Vertebrate photoreceptors are highly polarized sensory cells in which several different ionic currents have been characterized. In the present study, we used whole-cell, voltage-clamp and optical imaging techniques combined with micro-surgical manipulations to investigate the spatial distribution of ion channels within isolated salamander rods. In recordings from rods with visible terminals, evidence for five previously-identified ionic currents was obtained. These include two Ca²⁺-dependent currents, i.e. a Ca²⁺-dependent chloride current I_Cl(Ca) and a large-conductance Ca²⁺-and voltage-dependent K⁺ or BK current I_K(Ca), and three voltage-dependent currents, i.e. a delayed-rectifier type current I_K(V), a hyperpolarization-activated cation current I_h, and a dihydropyridine-sensitive L-type calcium current I_Ca. Of these, I_Cl(Ca) was highly correlated with the presence of a terminal; rods with visible terminals expressed I_Cl(Ca) without exception (n= 125), whereas ~71% of rods (40/56) without visible terminals lacked I_Cl(Ca). More significantly, I_Cl(Ca) was absent from all rods (n= 33) which had their terminals ablated, and recordings from the same cell before and after terminal ablation led, in all cases (n=10), to the loss of I_Cl(Ca). In contrast, I_K(Ca), I_K(V), and I_h, remained largely intact after terminal ablation, suggesting that they arose principally from ion channels located in the soma and/or inner segment. The outward I_K(Ca) in terminal-ablated rods was reversibly suppressed on "puffing" a Ca²⁺-free extracellular solution over the soma, and was markedly enhanced by the L-type Ca²⁺ channel agonist, Bay K 8644 (0.1-2 M). These data indicate that rod photoreceptors possess discrete targeting mechanisms that preferentially sort ion channels mediating I_Cl(Ca) to the terminal.