We investigate the vibrational properties of zigzag and armchair single-wall carbon nanotubes (CNTs) using the molecular mechanics approach. The natural frequencies of vibration and their associated intrinsic vibration modes are obtained. The simulations are carried out for four types of zigzag nanotubes (5, 0), (6, 0), (8, 0), (10, 0) and three types of armchair nanotubes (3, 3), (4, 4), (6, 6). The universal force field potential is used for the molecular mechanics approach. The first five natural frequencies are obtained for aspect ratios ranging from 5 to 20. The results indicate that the natural frequencies decrease as the aspect ratios increase. The results follow similar trends with results of previous studies for CNTs using structural mechanics approach. (C) 2010 Elsevier B.V. All rights reserved.