The codiffusion of arsenic and phosphorus implanted in silicon has been investigated after annealing at 900 and 1000 °C for different concentrations of the dopants. Analysis of the profiles was performed using secondary‐ion‐mass spectroscopy, junction staining, and incremental resistivity and Hall measurements. The results do not evidence any direct interaction between the dopants. All the observed anomalous effects of the codiffusion, compared with the diffusion of the single elements by themselves, seem to be justifiable on the basis of the interactions between the dopants and the defects produced by ion implantation. In addition, it has been observed that the presence of a high concentration of As atoms makes the annealing of the implantation damage faster and strongly reduces the P transient‐enhanced diffusion. This effect favors the fabrication of graded shallow junctions with a high‐surface‐carrier concentration.