This is an open-label, multicenter, phase II study to evaluate the safety and efficacy of single-agent AT-101 in patients with relapsed or refractory B-cell malignancies. For the purpose of this study, B-cell malignancies can include one of the following disease sub-types: follicular lymphoma (FL), diffuse large b-cell lymphoma (DLBCL), mantle cell lymphoma (MCL), small lymphocytic lymphoma (SLL)/chronic lymphocytic leukemia. Patients will be enrolled according to disease subtype into one of four groups in two stages. The first stage of each group will enrolled 13 patients. If patients within any group experience disease response, an additional 14 patients will be enrolled into that group.