To gain insights into transcription factors defining neuronal identity, we generated transgenic mice carrying a 1.8 kb rat neuron-specific enolase (NSE) promoter fragment fused to an E. coli/acZ gene. Pour of seven transgenie families expressed transgene RNA in the nervous system but not in most other tissues. Histochemical analysis of adult brain from the two lines with highest/acZ mRNA levels showed neuron-specific, pan-neuronal B-galactosidase activity. Developmental RNA and histochemical analyses showed parallel onset of transgene and endogenous NSE gene expression in various neuronal cell types, although the magnitude of NSE mRNA accumulation later in development was not matched by the transgene. These results suggest that &-acting regulatory elements, subject to neuron-specific control, are located within 1.8 kb upstream from the NSF gene.