Despite higher hit rates for cell phone samples, inefficiencies in processing calls to these numbers relative to landline numbers continue to be documented in the U.S. literature. In this study, we propose one method for using cell phone provider information and Internet resources for validating number status. Specifically, we describe how we used ‘‘in network’’ options available from three major providers’ web sites to determine the validity of cell phone numbers. We tested differences in working number rates (WNRs) among valid and nonvalid numbers against a normal processing control group and determined that the WNR among valid numbers was approximately 14 percentage points higher than the WNR of the comparison group. This process also shows promise in reducing the effort required to determine working status and may provide a basis for developing screening tools for cell phones that capitalize on resources that are unique to this technology.