A simple system for cutting dendrites of single neurons without damaging the viability of the cell is described. The system utilizes a rapidly vibrating (100 Hz) micropipette (<1 microm tip diameter), which is dragged under direct visual control across the dendrite of a selected neuron. We used this system in a thin slice preparation to dissect the apical dendrites of rat hippocampal CA1 pyramidal cells. We then used the patch-clamp technique in the whole-cell configuration to record from the isolated somata of these cells and to inject a dye into them. Both a functional and an anatomical disconnection of the dendrites from their somata were verified.