The intra- and inter-laboratory variability of bioaccessibility tests were evaluated in synthetic fluids relevant to oral, inhalation, and dermal exposure. Using one defined protocol, five laboratories measured metal release from cobalt oxide, cobalt powder, copper concentrate, Inconel alloy, leaded brass, and nickel sulfate hexahydrate. Standard deviations of repeatability (sr ) and reproducibility (sR) were used to evaluate the intra- and inter-laboratory variability, respectively. Examination of the sR:sr ratios demonstrated that, while gastric and lysosomal fluids had reasonably good reproducibility, other fluids did not show as good concordance between laboratories. Relative standard deviation (RSD) analysis showed more favorable reproducibility outcomes for some data sets, overall results varied more between than within-laboratories. RSD analysis of sr showed good within-laboratory variability for all conditions except some metals in interstitial fluid. In general, these findings indicate that absolute bioaccessibility results in some biological fluids may vary between different laboratories. Since measures of relative bioaccessibility are typically used (e.g., in read-across approaches for hazard and risk assessment), both inter- and intra-laboratory reproducibility are relevant unless all substances are tested in the same laboratory. Deviations in protocol interpretation may provide an explanation for some of the inter-laboratory variability observed.