Malachite green (MG) is a triphenyl methane dye used in various fields that demonstrates high toxicity to bacteria and mammalian cells. When bud stage zebrafish embryos were treated with MG at 125 150 and 175 ppb for 14 h, the development of trunk including intersomitic vessels was inhibited in MG-treated fk-1-GFP transgenic embyos. MG clearly induced whole growth retardation. MG induced severe cell death in trunk intersomite region of zebrafish embryos and in human vascular endothelial cells in a dose-dependent manner. MG inhibited heart rates and cardiac looping. MG attenuated whole blood formation and inhibited vascular endothelial growth factor (VEGF)-induced receptor (R)2 phosphorylation in vascular endothelial cells. In conclusion, MG significantly alters the cardiovascular development causing growth retardation in zebrafish through the blocking VEGFR-2 activation in early cardiovascular development. It suggests that MG may be an environmental toxic agent with the potential to induce embryonic cardiovascular defects in vertebrates (C) 2009 Elsevier Inc. All rights reserved.