Cross sections for target atom and projectile ion K vacancy production have been measured using solid targets of Mo, Ag,and Sn bombarded by 10 MeV/amu beams of H, Ne, Ar, Cr, Kr, Mo, Ag, Sn, Xe, Nd, Ho, Ta, Au, and Bi. It was found that the target K vacancy production cross sections reach a local maximum as the projectile atomic number Z1approaches the atomic number Z2of the target. In this work, the measured cross sections are compared to the results of calculations based on existing theories of K‐vacancy production. It was found that the predictions of current theories of the molecular orbital mechanism describe the shape of the Z1‐dependence of the cross sections in the near‐symmetric collision regime reasonably well. The contributions from direct electron capture and ionization were represented by a second‐order polynomial in Z1because the validity of available theoretical descriptions of these processes does not extend into the near‐symmetric region. © 2003 American Institute of Physics