2-photon microscopy has enabled real-time fluorescence imaging from the brains of living animals with cellular and sub-cellular resolution. By combining 2-photon microscopy with whole-cell patch-clamp techniques to load calcium indicator dyes, 2-photon microscopy can be used to monitor calcium transients in the dendrites of individual neocortical pyramidal neurones. Over the past several years I have been using these techniques to explore the roles of voltage-activated channels in dendritic function in anaesthetized and, more recently, awake animals. Imaging in intact animals obviously presents a number of technical hurdles, such as movement of the preparation. I will highlight how some of these barriers have been overcome and present some of the results that I have obtained using these techniques. Using these techniques, we have established that action potentials backpropagate into the dendritic trees of neocortical pyramidal neurones in urethane-anaesthetized rats, much as in slice preparations and that the effect of ongoing synaptic activity is minimal. More recently, I have extended 2-photon imaging techniques to the awake, head-restrained rat. Here I observed spontaneously occurring calcium transients occurring every 5 seconds (on average) in the proximal apical dendrite (range: every 3-15 seconds, n = 5 neurons; imaging 80-100 mm from the soma). The amplitudes of these transients were variable. Comparison with measurements from anaesthetized animals, suggest that they result from single or bursts of backpropagating action potentials. Backpropagation of single action potentials into more distal dendritic branches (150-200 mm from the soma) was also observed. However, the frequency of spontaneous transients was lower in distal than in proximal dendrites. This could be due to changes in the strength of backpropagation with different awake states or may simply result from a failure to detect some small calcium transients in distal dendrites. Hence in awake rats dendritic channels support active propagation of action potentials, much as reported in slice preparations and in anaesthetized rats. Many possible roles of dendritic channels in synaptic integration have been identified in slice preparations. Which of these roles contribute to synaptic integration in awake animals is unclear, but 2-photon microscopy is likely to prove one of the most useful tools with which we can investigate this question.