We conducted a randomized controlled trial, enrolling low-income uninsured adults to determine whether cash incentives are effective at encouraging a primary care provider (PCP) visit, and at lowering utilization and spending. Subjects were randomized to four groups: untreated controls, and one of three incentive arms with incentives of $0, $25, or $50 for visiting a PCP within six months of group assignment. Compared to the untreated controls, subjects in the incentive groups were more likely to have a PCP visit in the initial six months. They had fewer ED visits in the subsequent six months, but outpatient visits did not decline. We also used the exogenous variation generated by the experiment to obtain causal evidence on the effects of a PCP visit. We observed modest reductions in emergency department use and increased outpatient use, but no reductions in overall spending.