In an attempt to better understand the role of endothelial cells during HIV-1 infection, we report a virological and ultrastructural study on isolated endothelial cells from human adipose tissue, infected by HIV-1 in vitro. Supernatants from cultures showed the presence of p24 antigen and reverse transcriptase activity starting two days after HIV inoculation. A significant decrease of viral rescue was observed in cycloheximide treated cells confirming a de novo synthesis of viral products. SEM analysis individualized several surface slender projections and interdispersed virus-like particles in the infected cells. Furthermore, transmission electron microscopy (TEM) results showed cellular aspects of HIV phagocytosis and virus budding, suggesting that endothelial cells may represent a CD4 negative cell target of HIV-1 infection.