Genistein is a natural product found in soy beans; its consumption has been associated with a low incidence of metastatic prostate cancer. Genistein is a known protein-tyrosine kinase inhibitor, and in preclinical studies it has been shown to increase cell adhesion. Increases in cell adhesion in vivo would phenotypically reverse the first step in the metastatic cascade, potentially preventing metastasis formation, and is consistent with epidemiologic findings. This study seeks to determine the pharmacokinetics of genistein in humans by administering a single dose of genistein and performing a pharmacokinetic analysis. Patients will be treated with two formulations of genistein (a 43% genistein preparation or a 90% preparation). This is a phase I study, and patients will be treated on one of three dosing levels. Patients will be randomly assigned to receive one formulation first, followed by a washout period, and will then receive the second preparation (i.e. a randomized cross over design). Information from this study will be used to optimally design a multiple dose study wherein patients will be treated for longer periods of time.