The formation of vascular tubules by EA.Hy926 endothelial cells was studied in the presence of placental secretory products from women with normal gestation at early and late periods and with gestosis. The factors secreted by placental tissues at the early stages of placental development stimulated the branching angiogenesis, while the products of the end of pregnancy stimulated nonbranching angiogenesis. In gestosis the placental tissue secreted products stimulating even more intense nonbranching angiogenesis, which manifested by a lesser number of branchings of vascular tubes formed by EA.Hy926 endothelial cells.