OBJECTIVE 1p/19q co-deletion is a well-established tumor cell specific chromosomal abnormality in oligodendroglial tumors. The endothelial cells (ECs) of oligodendroglial tumor vessels are considered to be normal cells that do not acquire mutations. METHODS A total of 30 samples from 16 male and 14 female patients (median age of 46.5 years) with a histological diagnosis of primary anaplastic oligodendroglioma (AO) were collected in the study. The immunofluorescence technique was used to identify vascular ECs, and the 1p/19q status was detected with fluorescence in situ hybridization. Kaplan-Meier plots were compared using the log-rank method. RESULTS The ECs in AO had a higher 1p36 (detected signal) deletion rate than 1q25 (reference signal) (p < 0.01) and a higher 19q13 (detected signal) deletion rate than 19p13 (reference signal) (p < 0.01). The survival analysis results showed that both the progression-free survival (PFS) and overall survival (OS) of the patients with 1p/19q-co-deleted ECs were significantly longer than those with 1p/19q-intact ECs (PFS, p < 0.001; OS, p < 0.001). This correlation was validated by an independent cohort. In addition, the Cox regression model revealed that 1p/19q co-deletion in ECs was an independent prognostic factor (HR 0.056 [95% CI 0.012-0.261], p < 0.001 for PFS; HR 0.061 [95% CI 0.013-0.280], p < 0.01 for OS). CONCLUSIONS 1p/19q co-deletion and polysomy can be also found in the ECs of AO, which suggests that the ECs are, in part, tumor related and reflect a novel aspect of tumor angiogenesis.