Measure and compare the percentage of prescriptions fully dispensed to persons with and without Popular Health Insurance (SPS in Spanish) who use ambulatory and general hospital services associated with the Mexico State Health Services (SESA in Spanish), and taking into account insurance status. SESA user satisfaction was also measured with respect to access to medication.Information for the study was taken from four surveys of SESA ambulatory and hospital units that included probabilistic samples with state representativity. Samples of ambulatory units were selected by stratification according to level of care and association to the SPS service network.The findings indicate that the percentage of prescriptions fully dispensed in SESA ambulatory units has improved, reaching approximately 90%, especially among those units offering services to persons affiliated with SPS. Nevertheless, these percentages continue to be lower than those of ambulatory units associated with social security institutions. Percentages of prescriptions fully dispensed have also improved in SESA hospital units, but continue to be relatively low. In nearly all states, as the percentage of prescriptions fully dispensed has increased, user satisfaction with access to medication has also improved.In 2006 more than 50% of the states had high levels of fully dispensed prescriptions among persons with SPS (> or =90%). The more significant problem exists among hospitals, since only 44% of users who received a prescription in SESA hospitals in 2006 had their prescriptions fully dispensed. This finding requires a review of SPS medication policies, which have favored highly prescribed low-cost medications at ambulatory services at the expense of higher cost and more therapeutically effective medications for hospital care, the latter having a greater impact on household budgets.