Stimulation of endothelial cells (ECs) by growth factors, the subsequent degradation of the extracellular matrix and migration and proliferation of endothelial cells is thought to be an essential mechanism during angiogenesis. Several angiogenic growth factors, such as vascular endothelial growth factor (VEGF) and basic fibroblast growth factor (bFGF) are known to provide EC survival and proliferation. Our aim was to examine the effects of skeletal muscle cell conditioned medium infected by bFGF on HUVEC proliferation and angiogenesis. We constructed a replication-defective adenovirus (Ad/bFGF) and obtained conditioned medium from skeletal muscle cells (SkMCs) infected by Ad/bFGF. To determine effect of secreted factors from SkMCs infected with bFGF gene, HUVEC was cultured in the uninfected conditioned medium (control), Ad/LacZ infected conditioned medium (LacZ-CM) or Ad/bFGF infected conditioned medium (bFGF-CM) for 6 day. HUVEC cell proliferation, as determined by a MTT assay, more quadrupled in the bFGF-CM than in the LacZ-CM. These effects were not inhibited by neutralizing antibody to bFGF. For identifying the biological properties of other factors which are present in the bFGF-CM, concentrated sample was applied by SDS-PAGE and four protein bands were analyzed by MALDI-TOF MS and data base search. Several proteins were identified as matrix metalloproteinase-1 (MMP-1), cysteine proteases cathepsin L and plasminogen activator inhibitor-1 (PAI-1). These results suggest that skeletal muscle cells infected with bFGF produce soluble substances that contribute to HUVEC proliferation and angiogenesis.