The laminins belong to a family of trimeric basement membrane glycoproteins with multiple domains, structures, and functions. Endothelial cells bind laminin-1 and form capillary-like structures when plated on a laminin-1-rich basement membrane matrix, Matrigel. Laminin-1 is composed of 3 chains, alpha1, beta1, and gamma1. Because laminin-1 is known to contain multiple biologically active sites, we have screened 156 synthetic overlapping peptides spanning the entire laminin gamma1 chain for potential angiogenic sequences. Only 7 of these peptides, designated as C16, C25, C30, C38, C64, C75, and C102, disrupted the formation of capillary-like structures by human umbilical vein endothelial cells on Matrigel. Dose-response experiments in the presence of 50 to 200 microg/mL showed that tube formation was prevented by most peptides at 150 and 200 microg/mL, except for C16, which showed strong activity at all concentrations. Active peptides promoted vessel sprouting from aorta rings and angiogenesis in the chick chorioallantoic membrane assay. In addition, the active peptides also promoted endothelial cell adhesion to dishes coated with 0.1 microg of peptide and inhibited attachment to laminin-1 but not to plastic or fibronectin. Four of the active peptides, C25, C38, C75, and C102, may have cell-type specificity with endothelial cells, since they did not promote PC12 neurite outgrowth or adhesion of B16-F10 melanoma and human submandibular gland cells. These results suggest that specific laminin gamma1-chain peptides have angiogenic activity with potential therapeutic applications.