Fluorescence imaging represents a powerful approach for the detection of intracellular Ca(2+) signals in vivo. With appropriate techniques, Ca(2+) signals can be recorded at many levels of complexity, ranging from large scale neuronal networks down to individual presynaptic boutons or postsynaptic spines. Here we review the applicability of genetically encoded Ca(2+) indicators for in vivo Ca(2+) imaging of neural function. We describe some of the recent progress in sensor design and evaluate the performance of the new family of Troponin C-based Ca(2+) indicators. Further, we analyze properties of Ca(2+) biosensors transgenically expressed in various experimental animal models and illustrate their use for measuring somatic and dendritic Ca(2+) signals in neurons of the mammalian brain.