OBJECTIVES: According to a mandate, all California pharmacies will be changing to a new “patient centered “prescription label beginning January 2011. An increase in label size may be needed to comply with possible additional information/format changes that are being considered. This cost consequence study explored the impact of label changes to California pharmacies and projected to all US pharmacies. METHODS: A cost model was built based on input from 3 experts. It included: 1) continuing costs:  bottle, cap or closure, label (dual web sheet paper vs. thermal roll, paper used, glue used), and 2) One-time costs:  software program, additional storage area and staff training.  Average additional costs for increasing bottle size from 13 dram to 30 dram, increasing label size and added adhesive was estimated to be 10.5 cents. A literature search conducted to estimate consequence of label change identified only two articles that addressed the impact of a new commercial label on health outcomes and medication safety. RESULTS: The additional costs to pharmacies for the new label would be close to $34 million ($372M for US) assuming 324 million prescriptions are filled by retail and mail order pharmacies annually in California (3.54 billion for US). On average, each of 6000 California pharmacies will incur additional costs of $5700 dollars each year. Software changes were assumed to be zero cost. Additional storage and employee training were dealt with differently by each pharmacy hence were used as parameters for a sensitivity analysis. The two studies on consequence did not show any significant difference in impact on outcomes between using the new label and a traditional label. CONCLUSIONS: Additional costs of label change per pharmacy may not be considered significant; however these costs could be transferred to patients as pharmacies are already experiencing financial constraints.