Abstract. Purpose: To examine whether vascular endothelial growth factor (VEGF) as one of the most important intraocular cytokines for angiogenesis and increased vascular permeability is associated with Coats' disease. Methods: The clinical interventional study included 28 patients with Coats' disease and seven control patients with congenital cataract. During intraocular surgery, we obtained aqueous humour samples in which the VEGF concentration was measured by double-antibody sandwich enzyme-linked immunosorbent assay (ELISA). Coats' disease was graded into four stages. Results: The mean aqueous VEGF level was significantly higher in the Coats' study group than in the control group (158 +/- 88 versus 97 +/- 21 pg/ml; p = 0.002). The VEGF concentrations increased significantly (p < 0.001) from 91 +/- 32 pg/ml in Coats' disease stage 2 to 100 +/- 37 pg/ml in stage 3A1, 185 +/- 56 pg/ml in stage 3A2 to 256 +/- 93 pg/ml in patients with stage 3B. Vascular endothelial growth factor concentrations in Coats' stage 2 and 3A1 did not differ significantly from the values in the control group. Parallel to the association with the stage of the diseases, the VEGF concentrations were significantly (p < 0.001) correlated with extent of exudative retinal detachment. Conclusions: Increasing severity of Coats' disease is significantly associated with intraocular VEGF concentrations. These results favour the intravitreal application of anti-VEGF drugs as medical therapy of Coats' diseases.