The range profile for the combination implantation of10B and11B into the three stable isotopes of silicon28Si,29Si, and30Si in the energy range between 1 and 50 keV, has been studied by using the Monte Carlo simulation programtrim. It is found that for a given boron isotope, the implantation profile depends strongly on the isotopic state of silicon. The presence of the least abundant isotopes29Si and30Si, in silicon of natural abundance, influence considerably the range profile.