Correspondence to:

In their very comprehensive review on methods for assessment of occupational exposure in case-control studies Teschke et al. state that "among the exposure estimation methods in common use today, expert assessment is usually the best approach". They do so, despite the fact that it is well known that subjective assessments by experts is of a relative nature(1) and that in order to have a more quantitative assessment the experts have to be calibrated.(2, 3) The main reason for choosing experts can be traced back to the alternative methods of self-reported exposures and generic job exposure matrices (JEM) which as they claim suffer from severe limitations. Recently, the limitations and possibilities of exposure assessment on the basis of JEM were extensively discussed.(4) From a somewhat broader perspective, expert assessment and JEM are not as different as often is being suggested. A study in which an expert judges the job history of every case and control, is actually applying a very detailed (job) exposure matrix where the input axis is made up by exposure determinants which the expert think of as being important. The problem with the case-by-case expert assessment is that the process of assignin