The mouse TEN-M/ODZ proteins belong to a new family of type II transmembrane proteins with unknown function. The family consists of four members, which are expressed highly in brain and less in many other tissues. In the present study we have generated specific RNA probes and antibodies to characterize the expression of the 4 Ten-m/Odz genes in the developing and adult central nervous system (CNS) of mice. Ten-m/Odz3 and Ten-m/Odz4 mRNAs were first detectable at E7.5, Ten-m/Odz2 expression started at the 37 somite (E 10.5) stage, while Ten-m/Odz1 mRNA is not found before E15.5. In the adult mouse CNS mRNAs of the 4 Ten-m/Odzs were expressed in distinct patterns, which partially overlapped. Immunostaining and in situ hybridization localized proteins and mRNAs of Ten-m/Odzs in adjacent areas suggesting that TEN-M/ODZ proteins might be transported from the cell body along the axon or that they are shed from the cell surface and diffuse into distant regions.