Two recent studies have suggested that a schizophrenia susceptibility locus may lie on the proximal long arm of chromosome 5. Partial trisomy of a 20-30 centimorgan region of chromosome 5 (5q11.2-13.3) was found to cosegregate with schizophrenia in a Canadian family of Chinese descent. Moreover, DNA markers from proximal 5q (D5S39, D5S76) were found to be linked to schizophrenia and related disorders in seven British and Icelandic families. We now report an initial physical map of DNA markers relative to the partial trisomy chromosome 5, as well as preliminary evidence against linkage of this region to schizophrenia in four American families.