A quite simple formula for the thermal conductivity enhancement in carbon nanotube composites is presented based on a conventional model. This simple formula predicts much higher thermal conductivity enhancement even in the dilute case of the carbon nanotubes, due to ultrahigh thermal conductivity and aspect ratio of the carbon nanotubes. By applying this model to nanotube suspensions recently reported in the literature, we show that the conventional model is still valid for the nanotube-based composites. (C) 2003 Elsevier Science B.V. All rights reserved.