In order to identify genes regulated by vasoactive intestinal peptide, we performed differential display PCR as originally described by Liang and Pardee. Messenger RNA of PC12 cells treated with vasoactive intestinal peptide or nerve growth factor for one hour was reverse transcribed and amplified using different sets of oligo-dT and random primers. Radioactively labeled PCR products were displayed on polyacrylamide gels and candidate cDNAs extracted from the gel, re-amplified by PCR, cloned, and sequenced. Differential expression was verified by RT-PCR applying sets of specific primers obtained from the sequence. The specificity of the PCR product was confirmed by Southern blotting using a radioactively labeled internal primer and semi-quantitative densitometric analysis. This rapid and sensitive protocol led to the isolation of two immediate early genes, pip92 and PC4, known to be increased on mRNA level by nerve growth factor in PC 12 cells.