In this study, lead (Pb) bioaccessibility in contaminated soils was assessed using an in vitro method (SBRC) encompassing gastric (SBRC-G) and intestinal (SBRC-I) phases. Initially, bioaccessibility studies were performed with a Pb reference material (Pb acetate, 1-10 mg L(-1)) in order to determine the influence of pH on Pb solubility. In the gastric phase (pH 1.5), Pb solubility was 100% (100 +/- 2.9%, n = 16) irrespective of the Pb concentration added, however, when the pH of the intestinal phase was increased to near neutral, Pb solubility decreased to 14.3 +/- 7.2%. In contaminated soils, Pb bioaccessibility varied from 35.7 to 64.1% and 1.2 to 2.7% for SBRC-G and SBRC-I phases, respectively. When relative bioaccessibility (Rel-SBRC-I) was calculated by adjusting the dissolution of Pb from contaminated soils by the solubility of Pb acetate at pH 6.5 (intestinal phase pH); Rel-SBRC-I values ranged from 11.7-26.1%. A stepwise regression model based on Pearson correlation factors was used to determine the suitability of in vitro assays for predicting in vivo (swine assay) relative Pb bioavailability. Rel-SBRC-I provided the best estimate of in vivo relative Pb bioavailability for soils used in this study (in vive relative Pb bioavailability [%] = Rel-SBRC-I [pH 6.5%] x 0.58 + 1.98, P = 0.53). The versatility of Rel-SBRC-I was demonstrated by accurately predicting relative Pb bioavailability from other reported in vivo studies.