Sampling behavior of multielements in a stream sediment matrix was studied with sample sizes in a range of 9 orders of magnitude by a combination of INAA, PIXE and SR-XRF. For accurately weighable sample sizes (>1mg), sampling uncertainties for 16 elements are better than 1% by INAA. For sample sizes that cannot be accurately weighed (<1mg), PIXE and SR-XRF were used and the effective sample sizes were estimated. Sampling uncertainties for seven elements are better than 1% at sample sizes of tenth mg level, and that for three elements are better than 10% on ng levels.