Organic field-effect transistors containing pentacene or α sexithiophene on random arrays of carbon nanotube bundles were fabricated. The impact of nanotube bundles on the performance of devices with different geometries and surface treatments was studied. Upon incorporation of an appropriate amount of nanotube bundles, we observed an increase in the "effective" field effect mobility as high as 20 times while maintaining the high on/off ratios. Furthermore, our preliminary results show that nanotube bundles might template the growth of organic crystals under certain conditions, resulting in the formation of organic nucleates with preferred orientations.