We have refined the location of the Brn-3a genomic locus (POU4F1), using somatic cell hybrid analysis, to 13q21.1-->q22. Furthermore, we have shown that two YACs, known to contain the closest marker linked to neuronal ceroidlipofuscinosis (CLN5), also contains the Brn-3a gene. As one of these YACs is only 320 kb long, this localises POU4F1 within the critical region defining the CLN5 locus, and raises the possibility that POU4F1 is a candidate gene for CLN5.