Ependymins are unique, brain specific glycoproteins, which are major constituents of the cerebrospinal fluid. Originally, they were discovered in goldfish and are thought to be involved in synaptic plasticity. In the present study two transcripts were characterized in Brachydanio rerio originating from a single gene possibly by alternative splicing. These transcripts differ only in the length of their 3'-non-coding-regions and the encoded protein shares 90 and 88% homology with the two corresponding goldfish proteins, respectively. In situ hybridization revealed the expression of ependymins exclusively in the leptomeninx including its invaginations but not at all in the ependymal layer surrounding the ventricles. An initial developmental profile showed that ependymins first appear before hatching, i.e. between 48 and 72 h postfertilization.