The calcitonin/CGRP gene is transcribed in thyroid C cells and some neuronal cells but not in other cell types. Although the promoter sequences mediating gene activity in thyroid C cells have been extensively studied, the elements responsible for promoter activity in neuronal cells and its stimulation by nerve growth factor (NGF) have not previously been defined. We report the first use of the calcium phosphate procedure to successfully transfect adult rat dorsal root ganglion neurons, which naturally express the calcitonin/calcitonin gene-related peptide (CGRP) in an NGF-inducible manner. This method was used to characterize the elements in the calcitonin/CGRP promoter which are responsible for its basal activity and NGF inducibility in DRG neurons and in PC12 cells, a neuronally derived cell line which does not naturally express the calcitonin/CGRP gene. Although the sequences required for basal activity are similar in each cell type, we show that a minimal calcitonin/CGRP promoter is NGF-responsive in dorsal root ganglion cells, but that upstream sequences are required for such inducibility in PC12 cells.