The design of appropriate studies to assess the sensory irritant and neurobehavioral effects of exposure to complex VOC mixtures poses a variety of methodological challenges, particularly at the low levels found in new buildings. For instance, Otto et al (1989) exposed subjects to a 25 mg/m3 mixture of 22 VOCs representative of the highest concentration encountered in new homes. The concentration is equivalent, in mass, to about 7 ppm toluene. As one might predict, the mixture produced no consistent effects on the performance of an extensive neurobehavioral test battery, but did elicit classical SBS symptoms of eye and throat irritation, headache and fatigue. Failure to find functional deficits could be due to several factors. Perhaps the tests were not sensitive (or difficult) enough to detect effects. The authors used the neurobehavioral evaluation system which was designed for occupational field studies. Further study is needed to determine the optimal testing parameters for use in repeated-measure laboratory studies of university students. Further study is also needed to determine which subsets of the population are most vulnerable to adverse effects of VOC exposure. Finally, other physiological endpoints (e.g., measures of inflammation and pulmonary function) need to be explored.