Effects of variation in age and mating status on dispersal of the twospotted spider mite, Tetranychus urticae Koch (Acari: Tetranychidae), from fenvalerate-treated leaf surfaces were investigated. Unmated and mated female mites, 1 to 6 days in age, were scored for walkoff and spindown dispersal response on bean leaves treated with a sub-lethal, residual dose of fenvalerate. Variation in mite age ... [Show full abstract] did not have a pronounced effect on dispersal response. Significant differences in dispersal response due to mating type were observed, yet the mean differences in dispersal response between unmated and mated females was generally small. Our data suggest that the current practice of using mated female mites of unknown age when testing for among-population differences in dispersal response, in most cases, provides an adequate estimate of population response when differences among treatments in dispersal response are large. However, when testing for within-population differences in dispersal response, small treatment effects may be more easily measured using a single age class of mites, because this could decrease within-treatment variance.