Uniquely, olfactory neurons continuously replace themselves. Olfactory bulb ablation induces coordinated degeneration and regeneration in olfactory neuroepithelium; up-regulated growth factors bind to their receptors, initiating a phosphorylation cascade activating mitogen-activated protein kinases (MAPK). MAPK then relay proliferation signals to the nucleus. Mitogen-activated protein kinase phosphatase-1 (MKP-1) inactivates MAPK. We examined MKP-1 expression in adult mouse olfactory epithelium following bulbectomy using a reverse transcription-polymerase chain reaction (RT-PCR) as well as Western analysis. While MKP-1 expression was high in olfactory epithelium from control mice, it decreased greatly 2–3 weeks after bulbectomy in temporal association with increased tyrosine phosphorylation of MAPK. Thus, reduced MKP-1 expression may contribute to regeneration of olfactory neuroepithelium after bulbectomy via decreased dephosphorylation of MAPK.