The noise exposure of truck drivers was measured during normal commercial payload runs with special instruments, which are equipped with subminiature microphones. These can be mounted within the cavum of the concha, where measurements are least affected by extraneous effects.By means of these instruments sound levels were continuously recorded within both ears of the driver and at the centre of the cab. Analysis of results shows that the driver’s exposure is highest during freeway hauls and that permanent hearing loss hazard may exist. Frequent use of radio or CB radio can significantly increase this hazard. It is also evident that the sound levels measured within the ears of the driver are generally significantly higher than at the centre of the cab.