  Assisted chaotic inflation in brane cosmology is discussed. We work in the
framework of Randall-Sundrum (RS) II model, in which adopting the RS condition
the only parameter is the five-dimensional Planck mass. Using the scalar
spectral index and the amplitude of scalar perturbations we determine both the
mass of the scalar fields responsible for inflation and the fundamental Planck
mass of the higher-dimensional theory. We find that the mass of the scalars has
the typical value of the inflaton mass in chaotic inflation ($M_I \sim 10^{13}$
GeV) and that the five-dimensional Planck mass is very close to the GUT (Grand
Unified Theories) scale ($M_5 \sim (10^{16}-10^{17})$ GeV). Furthermore, no
matter how many scalar fields we use it is not possible to have chaotic
inflation with field values below the fundamental Planck mass.
