Recently, C-60 fullerene molecules have been observed inside carbon nanotubes. Here, we calculate the cohesive properties of fullerene-filled ropes of (10,10) nanotubes. The calculation is based on the Lennard-Jones 6-12 potential for interactions between carbon atoms on the surfaces of interacting molecules. The results are compared to the cohesive properties of unfilled ropes. It is found that filling ropes of (10, 10) nanotubes with C60 fullerene molecules increases the cohesive energy by 15%, the bulk modulus by 10%, while the intertube spacing does not change. The possibility Of C-60 molecules in adjacent tubes being ordered is also investigated. (C) 2002 Elsevier Science B.V. All rights reserved.