Symptomatic craniospinal dissemination of glioblastomas is considered rare, and unambiguous pathologic or molecular predictors of tumor leptomeningeal spread remain to be defined. We performed molecular analysis of 8 glioblastomas with symptomatic leptomeningeal dissemination by using fluorescence in situ hybridization and array-based comparative genomic hybridization (array-CGH). The most frequently encountered alteration was gain of the 1p36 locus, which was found in all 8 samples examined. Array-CGH analysis of 3 available samples also disclosed numerous gains at the 1pter-p36.1 locus involving at least 3 DNA clones from this chromosomal region. Consequently, an analysis of 1p copy number status might be kept in mind as an additional tool for further predicting the clinical course of glioblastoma.