Infantile neuronal ceroid lipofuscinosis, INCL, CLN1, is an autosomally inherited progressive neurogenerative disorder. The disease results in the massive death of cortical neurons, suggesting an essential role for the CLN1 gene product in the normal neuronal maturation during the first years of life. Identification of new multiallelic markers has now made possible the construction of a refined genetic map encompassing the CLN1 locus at 1p32. Strong allelic association was detected with a new, highly polymorphic HY-TM1 marker. We incorporated this observed linkage disequilibrium into multipoint linkage analysis, which significantly increased the informativeness of the limited family material and facilitated refined assignment of the CLN1 locus.