AbstractThe ontogeny and cellular specificity of expression of β‐galactosidase activity and olfactory marker protein (OMP) are compared in olfactory tissue of the H‐OMP‐lacZ‐3 line of transgenic mice. In this line the expression oflacZis driven by a 0.3 kb fragment of the rat OMP promoter. During fetal development,lacZexpression is detectable in olfactory receptor neurons (ORNs) shortly after the initial appearance of endogenous OMP. The β‐galactosidase marker was observed only in mature olfactory receptor neurons where it co‐localized with endogenous OMP. It was absent from immature neurons that express the growth associated phosphoprotein B50/GAP43. Lesion of the peripheral olfactory pathway by intranasal irrigation with Triton X‐100 eliminated expression of both OMP andIacZin the olfactory neuroepithelium. Subsequent regeneration of the full complement of olfactory receptor neurons was associated with co‐expression of both OMP and β‐galactosidase activity. Neither OMP nor β‐galactosidase activity was induced in any other cell type of the regenerating olfactory mucosa. Thus, as little as 0.3 kb of the OMP promoter has the ability to targetlacZexpression to olfactory receptor neurons in a temporally and spatially defined manner. We discuss the potential utility of this transgenic line for future studies of the olfactory system.