Overexpression of ErbB2 has been frequently found in mammary carcinoma. We have previously shown that the aberrant activation of H-Ras induces human breast cell invasion and migration. The present study was aimed at investigating the effect of ErbB2 overexpression on H-Ras-induced breast cell invasion and to elucidate the underlying mechanisms. Herein, we show that overexpression of ErbB2 promotes invasive and migratory abilities of H-Ras-activated MCF10A human breast epithelial cells through upregulation of matrix metalloproteinase (MMP)-13 and urokinase-type plasminogen activator (uPA). We also demonstrate that the p38 MAPK is an important signaling molecule in the ErbB2-induced upregulation of MMP-13 and uPA and invasion/migration of H-Ras MCF10A cells overexpressing ErbB2. The present study elucidating the molecular mechanism underlying ErbB2-induced promotion of H-Ras MCF10A cell invasion may provide invaluable information for understanding breast cancer progression and establishing therapeutic interventions for breast cancer.