This is an open-label phase I/II study that will investigate the combination of dasatinib and rituximab therapy in patients with relapsed/refractory CLL. In phase I, eligible subjects will take either 100 mg or 140 mg of dasatinib daily along with rituximab on day 1 of each cycle for 6 cycles. In phase II, eligible subjects will all receive the same dose of dasatinib, as established in the phase I portion, along with rituximab on day 1 of each cycle for 6 cycles.